- This article is in the process of revision and expansion.
Colonel Benjamin Tallmadge, leader of the Culper Ring, in a 1790 portrait with his son William
|Type||military spy ring|
|Purpose||to provide military intelligence from British-occupied New York|
|Headquarters||Setauket and New York City|
|Colonel Benjamin Tallmadge|
|Abraham Woodhull, Robert Townsend, Caleb Brewster, Austin Roe|
The Culper Ring was a spy ring organized by American Major (later Colonel) Benjamin Tallmadge under orders from General George Washington in the summer of 1778 during British occupation of New York City at the height of the American Revolutionary War. The "Culper" name was suggested by Washington who devised it from Culpeper County, Virginia. The two main members of the Ring, Abraham Woodhull and Robert Townsend, used "Samuel Culper, Sr." and "Samuel Culper, Jr." respectively, as aliases. Tallmadge was in direct contact with and control of the Ring but Washington often directed its operations. Tallmadge was referred to by the alias of "John Bolton."
The Ring's task was to send messages to General Washington about the activities of the British Army in New York City, the British headquarters and base of operations. The members of the Ring operated mostly in New York City, Long Island, and Connecticut. The Ring's covert operations started in about late October 1778 and continued through the British evacuation of New York in 1783, but its heyday was between 1778 and 1781.
The Culper Ring provided valuable information to General Washington including that the British planned a surprise attack on the newly allied French forces under Lieutenant General Rochambeau at Newport, Rhode Island, before the French could fully recover and set up defenses after their arduous sea journey to America; that the British planned to counterfeit American currency on the actual paper used for the Continental dollars, prompting the Continental Congress to retire the bills; that British Major General William Tryon's raid in Connecticut in July 1779 was a diversion to induce Washington to divide his forces so British Lieutenant General Sir Henry Clinton could attack them piecemeal; and that a high ranking American officer, soon shown to be American Major General Benedict Arnold, had been plotting with British Major John Andre to surrender the garrison and to turn over the vitally important American fort at West Point, New York, on the Hudson River to the British. The Culper Ring is often credited for the exposure of an attempt on Washington's life, but as no official record of an attempt exists, it is conjecture.
- 1 Background
- 2 Establishment of the Culper Ring
- 3 Expansion of the Ring
- 4 Secrecy
- 5 Hercules Mulligan and Cato
- 6 Other persons identified as informants
- 7 Women in the Ring
- 8 Twentieth Century disclosure of the Ring
- 9 In popular culture
- 10 See also
- 11 Notes
- 12 References
- 13 External links
British Army occupation of New York City
Under pressure from American colonial forces, the British Army under General William Howe evacuated Boston, Massachusetts, on March 17, 1776 and sailed for Halifax, Nova Scotia, to reorganize. Before Howe's forces had completed their departure, American General George Washington had begun to move his troops to New York City, where most had arrived by mid-April to begin preparing defenses. Washington correctly suspected that Howe would return to New York City to make it the British base of operations.
General Howe's troop ships began to arrive at New York Harbor on June 28, 1776. On July 3, 1776, Howe's men began to land at undefended Staten Island. General Howe's brother, Vice Admiral Richard Howe, arrived the following week to take charge of the British naval force. British and Hessian soldiers continued to arrive until August 12, 1776. Washington did not have a spy network at New York that he could count on for intelligence as he could from the many Patriots that had previously organized to spy on the British Army at Boston. On the other hand, the British could depend on the many Loyalists at New York City for intelligence. So Washington divided his smaller force in order to defend several possible locations on Long Island and Manhattan Island, where the British might attack.
When General Howe had all of his forces in place, his initial moves did not alert Washington to the full danger that the Continental Army faced because Washington's intelligence operatives seriously underestimated British troop strength. On August 22, 1776, British Army troops from Staten Island landed on Long Island to begin the New York and New Jersey campaign to drive the Continental Army from New York City.
First, on August 27, 1776, the British overwhelmed the American defenders at the Battle of Long Island, forcing the Americans back to their fortifications on Brooklyn Heights. On August 30, 1776, before the British could attack the outnumbered and demoralized Americans, Washington's troops quietly withdrew from Long Island to Manhattan. On September 15, General Howe attacked the Continental Army force stationed at New York City, then located only on lower Manhattan, and landing at Kip's Bay, drove the Americans out of the city and captured all of the cannons they had there. Despite the American victory at the Battle of Harlem Heights the following day, September 16, 1776, Howe forced the Continental Army to abandon Manhattan entirely through a series of maneuvers and engagements, most significantly the Battle of Fort Washington, where the British took almost 3,000 prisoners on November 16, 1776.
By early December, the Americans had been forced to withdraw across New Jersey to Pennsylvania. The British controlled New York City and made it their military headquarters and base of operations until the war ended in 1783.
According to some sources, Washington's crucial successful attack on the Hessian garrison at Trenton, New Jersey, on December 26, 1776 was greatly aided by an American spy of Irish descent, John Honeyman, who provided information on the Hessian camp and the Hessians' planned Christmas celebration and gave the Hessians false intelligence about the condition of the Continental Army. In an article for the CIA's Studies in Intelligence Journal, however, Alexander Rose debunks the Honeyman story, tracing it to his daughter and grandson. Although the story had been widely accepted, Rose notes that David McCullough took no note of it in his book 1776. He also quotes Historian David Hackett Fischer in Washington's Crossing as stating "[The story] might possibly be true but in the judgement of this historian, the legend of Honeyman is unsupported by evidence. No use of it is made here."
Early American intelligence operations in New York City
Before Howe moved from Staten Island, Washington received information of varying utility from individual agents, such as Lawrence Mascoll, who obtained some intelligence on Staten Island before August 23. After evacuating his troops from Brooklyn Heights, Washington asked Brigadier General William Heath and New York militia general, soon to be Governor of New York and later Vice President of the United States George Clinton to set up "a channel of information" on Long Island. Washington did not yet try to establish permanent agents behind enemy lines. His next agent, the untrained and easily recognized Captain Nathan Hale, was captured during his effort to obtain intelligence in New York City by the cunning and ruthless Loyalist ranger, Lieutenant Colonel Robert Rogers, and summarily executed by the British on September 22, 1776.
By January 1777, Washington thought that civilians would attract less attention as spies and that they must recruit other agents to gather intelligence. He asked William Duer, a member of the New York Committee for Detecting and Defeating Conspiracies of the New York Provincial Congress to recommend someone to be the agent. Duer recommended a colleague, Nathaniel Sackett. Washington appointed Captain Benjamin Tallmadge, a classmate and friend of Nathan Hale, to be Sackett's contact with the army.
Tallmadge was promoted to major on April 7, 1777, his regiment was called from Connecticut to join the main body of the Continental Army and he had little time to devote to intelligence work. Sackett had developed some advancements and new methods for spying, such as keeping an agent in enemy territory and finding a means of regular communication, which he detailed in a letter to Washington on April 7, 1777, the date of Tallmadge's promotion. Sackett also recruited a few agents, whose identities remain unknown. He discovered that the British were building flat-bottomed boats to use in a campaign against Philadelphia. Sackett had not produced enough correct intelligence fast enough for Washington, however, and he was soon paid and dismissed. Early in 1777, American Colonel Elias Dayton set up a spy network on Staten Island to work in parallel with an established American intelligence agent, John Mersereau.
British Army occupation of and withdrawal from Philadelphia
Sackett was correct about Howe's intention to move against Philadelphia. Howe moved his force by water to Head of Elk, Maryland on Chesapeake Bay because he believed the American defenses on the Delaware River were too strong to attack. Washington failed to stop the British at the Battle of Brandywine on September 11, 1777 and the British took Philadelphia on September 26. The focus of intelligence gathering switched to Philadelphia and Washington assigned Major John Clark, who had returned to the army from successfully spying on Long Island but had been severely wounded in a skirmish before the Battle of Brandywine. Clark set up a successful network of spies but his unhealed wound and constant exertions wore him out and he had to retire to a desk job.
By the late Spring of 1778, the British found Philadelphia too difficult to supply and too vulnerable to attack. Their new commander-in-chief, General Sir Henry Clinton, was ordered to leave Philadelphia and defend New York City. France had allied with the Americans, which increased the possibility of an attack on the British at New York. Clinton began to evacuate Philadelphia on June 10, 1778. The Continental Army attacked the British during their return to New York at the Battle of Monmouth on June 28, 1778, hastening the British movement. Clinton's forces retreated to Sandy Hook, New Jersey and from there, they took ships for New York City, which they had already occupied for almost two years.
Establishment of the Culper Ring
The focus of intelligence gathering returned to New York, where Washington then lacked a spy network. On August 7, 1778, Washington received a letter from Lieutenant Caleb Brewster at Norwalk, Connecticut, with an offer to report on the enemy, to which Washington cautiously agreed and replied with advice. On August 27, Brewster sent his first report including the condition of British warships after a storm and some battles with French warships at the beginning of the Battle of Rhode Island. Brewster also reported that several regiments of British troops were boarding ships to take them to Newport, Rhode Island.
Washington assigned General Charles Scott to handle Brewster and find additional agents. He also asked Major Benjamin Tallmadge to assist Scott. Scott had many other duties and he found intelligence work uninteresting. So Tallmadge did most of the intelligence work and Washington soon directly asked Tallmadge to recruit people who could be trusted to collect intelligence in New York City.
Tallmadge recommended Abraham Woodhull of Setauket, in Suffolk County on Long Island as a contact for Brewster. Woodhull was a childhood friend of both Brewster and Tallmadge. A few months earlier, Woodhull had been taken prisoner by an American ship and charged with illegal trading, of which he was in fact guilty. He was held in Connecticut until Tallmadge quietly talked with Governor Jonathan Trumbull, who released Woodhull. Before Woodhull left Connecticut, Tallmadge spoke with him about joining Washington's secret service. In a dinner with Washington and Scott on August 25, Tallmadge convinced Washington that Woodhull was trustworthy. At that dinner the officers devised the alias "Samuel Culper" for Woodhull, with Washington suggesting Culper as a variation of Culpeper County, Virginia, where Washington had worked as a surveyor in his youth.
Tallmadge was not getting along well with the difficult Scott and their approaches to spying differed. Scott wished to continue using single mission agents to sneak in and out of enemy lines while Tallmadge favored embedding spies in enemy territory and establishing a secure line of communication back to base. When Scott lost three of five agents sent to spy on the British in New York City in early September, Washington decided that Tallmadge's method should be used, and as early as October 22, was communicating directly with Tallmadge about setting up a network with Woodhull and Brewster. On October 29, Scott resigned as chief of intelligence and Washington assigned Tallmadge to lead the intelligence network.
At first, Woodhull would go to New York City every few weeks to gather intelligence. The presence of Mary Underhill, his married sister, in the city gave Woodhull a reason to visit. On October 31, he was questioned at a British checkpoint, increasing his anxiety about the dangerous mission. Nonetheless, he returned to Setauket with valuable information about the British supply fleet. On November 23, 1778, Woodhull provided a precise report on the identity of British units, numbers of troops and dispositions in New York City, proving his worth as a spy. Woodhull soon recruited his brother-in-law, Amos Underhill, who ran a boarding house in the city with his wife Mary, to gather intelligence. But Underhill's reports were often too vague to be of much value.
At first, Woodhull had to return to Setauket to pass messages to Caleb Brewster to take to Tallmadge or to receive messages from Tallmadge via Brewster. By December 1778, Tallmadge set up couriers, at first Jonas Hawkins, then in the early summer mainly Austin Roe, who would take messages the 55 miles (89 km) between New York and Setauket to pass them to Brewster. The courier's task was to get the letters to Brewster who would pick up messages at one of six secluded coves near Setauket and, with his rotating whaleboat crews, take them across the Sound to Tallmadge at Fairfield, Connecticut. Tallmadge would then take them to Washington's headquarters. This time-consuming task was replaced in January 1779 by the assignment of express riders to take the messages from Tallmadge to Washington.
Local tradition claims that Anna Strong, a resident of Setauket and a friend and neighbor of Abraham Woodhull, helped pass along messages from the spy ring by posting pre-arranged signals to indicate when one of the spies was ready to submit intelligence. If Strong hung a black petticoat on her clothesline, it meant Brewster had arrived in town in his whaleboat. Next to that she would hang a quantity of white handkerchiefs. The specific number of handkerchiefs indicated one of six hiding places where Brewster might be located. Abraham Woodhull used Strong's signals to meet Brewster, or to drop messages, at one of the meeting-places. Historian Richard Welch writes that the tradition of the clothesline signal is unverifiable but it is known that the British had a woman at Setauket who fits Anna's profile under suspicion for disloyal activities.
Brewster occasionally would add his own report to the Culper messages. In a January 1779 report received by Washington in early February, Brewster sent some information about naval matters and boat building at New York City and warned that local Loyalists were outfitting privateers for operations on Long Island Sound.
Brewster's message about naval matters was with a message from Woodhull which precisely described the British regiments and commanders at the northern tip of Manhattan, totaling about 8,500 men. Woodhull also reported on British boat-building, confirming Brewster's report. Tallmadge and Washington thought that the boats might be to give New York Royal Governor and Major General (of Provincials) William Tryon, who already had conducted a raid during the winter, transport for an attack by water, possibly against Connecticut.
Through Spring 1779 Woodhull became increasingly anxious about being discovered and did little in May and June. On June 5, 1779, John Wolsey, a Long Island privateer who was captured by British, in order to secure parole, told British officers he had heard Abraham Woodhull was up to something dubious. While Woodhull was away in New York City, Colonel John Graves Simcoe, commander of the Queen's Rangers, came to Setauket to look for him. Not finding Woodhull at home, Simcoe's men attacked and beat Woodhull's father, Judge Richard Woodhull. Abraham Woodhull escaped arrest because a Loyalist militia officer, Colonel Benjamin Floyd, who had married a distant relative, Ruth Woodhull, a sister or cousin of New York militia Brigadier General Nathaniel Woodhull, vouched for him.
In late June 1779, Washington sent a letter to Tallmadge in which he identified George Higday as a possible operative to relieve Woodhull in New York City. The British had intercepted a June 13 letter from Washington referring to C_____s, "a liquid" and Tallmadge. On July 2, British cavalry under the command of Colonel Banastre Tarleton attacked Tallmadge's camp and captured his horse and some papers including the letter mentioning Higday. They were trying to capture Tallmadge himself because they now knew he was head of Washington's intelligence operation. The second letter, captured from Tallmadge, confirmed that an agent, C______, was operating in New York City and that Tallmadge was the chief intelligence officer for Washington. Higday escaped execution but would be of no use to Washington, or Clinton who tried to recruit him as a double agent, as a spy.
Woodhull reported that after the June incident at Setauket, he could not continue to operate in New York City because he was still under suspicion but he had a new agent for New York City lined up and would go to New York to finalize arrangements with him.
Expansion of the Ring
In June 1779, Woodhull engaged Robert Townsend, who used the alias "Samuel Culper, Jr.," to gather intelligence in New York City. Since Townsend was engaged in business there, his presence was expected to arouse less suspicion than Woodhull's visits would. He also had access to British officers through the authorship of a society column in a Loyalist newspaper and his tailoring business, as well as his interest in a coffeehouse with Loyalist newspaper owner James Rivington, who also was a secret member of the Ring.
After Townsend began his intelligence activities in New York City, Woodhull operated almost exclusively from Setauket. A revised communications network was then established in which Townsend would pass intelligence to a courier--- at first Hawkins, then Hawkins and Roe, and after September 1779, exclusively Roe---who would take it to Setauket and pass it to Woodhull, usually via dead drop in a box hidden in a field which Roe rented from Woodhull. Woodhull would evaluate and comment on it and pass it to Brewster, who would take it across Long Island Sound, occasionally adding an intelligence note of his own, and pass it to Tallmadge. Tallmadge would usually add a cover letter with comments.
As noted before, tradition holds and many sources state that Anna Strong signalled Brewster that a message was ready with a black petticoat on her clothesline in Setauket, which was easily visible by Brewster from a boat in the Sound and by Woodhull from his nearby farm. Tallmadge sent the messages, or received messages from Washington by a relay of dragoons, acting as couriers.
Hawkins at first was bold but became increasingly anxious about British patrols. His role was reduced between April 1779 when Woodhull identified both Hawkins and Roe as couriers for the Ring and July 1779 when Tallmadge gave Roe, but not Hawkins, a code number in his code directory.
Woodhull wrote in a coded message on August 15, 1779, that Hawkins had to destroy a letter from Culper, Jr., or be captured. In his August 15 message, Woodhull wrote that Hawkins insisted that his next meeting with Townsend be in an out of the way location. Townsend did not like taking the additional risk and was beginning to doubt Hawkins's reliability and to regret the destroyed messages. Finally in September 1779, with Hawkins increasingly anxious, and more importantly, with Townsend refusing to deal with him any longer, Hawkins stopped his courier services for the Ring. Woodhull acted as courier on September 11 so he could explain to Townsend the loss of the earlier letters. Austin Roe then became the sole permanent courier for the Ring.
Secrecy was so strict that Washington did not know the identity of all the operatives. Townsend, who was recruited by Woodhull, was especially insistent that his identity not be revealed, although of necessity Austin Roe, the Ring's main courier between New York City and Setauket, and his predecessor before September 1779 and occasional backup, Jonas Hawkins, needed to know Townsend.
Among the techniques the Ring used to relay messages were coded messages published in newspapers and invisible ink, called a sympathetic stain, to write between the lines of what appeared to be typical letters.
Perhaps with Nathan Hale in mind, Washington made sure the Culper Ring spies had more support and operated in greater secrecy. Through Tallmadge, he provided them with codes, dead drops, and aliases. Tallmadge, Woodhull and Townsend were given code names. They, along with Washington, Brewster, Roe and Rivington were given code numbers. George Washington's code number was 711.
Some sources note a female member of the ring, known only as Agent 355 while others believe that this code number referred to Anna Strong or was simply a misunderstanding of a cryptic reference in one of Abraham Woodhull's letters.
Hercules Mulligan and Cato
Hercules Mulligan was recruited to spy for the Continental Army in New York City by Alexander Hamilton. Mulligan was born in 1740 and was a friend of Townsend's father. Mulligan, an active member of the Sons of Liberty, had taken in Washington's aide, Alexander Hamilton, when he arrived in New York as an orphan in 1773 to attend King's College, later Columbia University, and had helped Hamilton obtain a commission in the army. He had a fashionable clothing business, near Robert Townsend's establishment, which along with his marriage to Elizabeth Sanders, daughter of a Royal Navy admiral, gave him access to officers who would talk to him about military matters.
Alexander Rose describes Mulligan as a "subagent of the Culper Ring." He wrote that Mulligan began his activities within six weeks of the date Townsend sent his first Culper letter. Mulligan, however, began his activities in late 1776 or early 1777, well before formation of the Culper Ring. Historian Stephen Knott says that Mulligan co-operated with the Culper Ring, but mostly operated as a lone agent. Alexander Rose states that Mulligan gave Townsend information, which Townsend added to his reports.
Mulligan's African-American slave, Cato, was his "faithful accomplice" in his intelligence activities, which began no later than April 1777, over a year before the formation of the Culper Ring. In January 1779, Cato delivered a message from Mulligan to George Washington's aide, Alexander Hamilton, that the British planned to kidnap or kill American leaders including Washington and New Jersey Governor William Livingston. Mulligan had received the information from his brother Hugh, who was with Kortright and Company, a contractor for British Army. Washington and Livingston took appropriate precautions.
When Mulligan was arrested on suspicion of espionage after the defection of Benedict Arnold to the British in New York, Townsend ceased his activities for a time for fear he also would be discovered. Woodhull passed on the information concerning Townsend's dejection and concern over the arrest of "one that hath been ever serviceable to this correspondence." Arnold did not have any hard evidence against Mulligan so he was released, but may have spent as many as five months, until February 1781, in prison. Author Harry Thayer Mahoney wrote that the British failure to lock up Mulligan except for a short time was a "failure of British counterintelligence."
Mulligan continued to pick up intelligence after his release. He discovered that the British planned to ambush Washington while he was on his way to a meeting with Rochambeau on March 5, 1781. Since Mulligan and Cato remained under suspicion and could not communicate directly with Washington's headquarters, Mulligan gave the information to Townsend, who sent it to Washington via the Culper Ring network. The message arrived in time for Washington to avoid the trap and travel to the meeting by another route.
Other persons identified as informants
The members of the ring gathered information from a variety of sources, including persons other than unwitting British officers. Some persons who were among those informants or associates, about whom little or nothing about their activities can be found in sources in which they are identified, included Joseph Lawrence, a Long Island resident, Captain Nathan Woodhull, Woodhull's uncle who served as a Loyalist militia officer but provided information to Abraham Woodhull, Nathaniel Ruggles, a schoolmaster and physician born in 1713, Joshua Davis, a Brewster deputy and occasional substitute, George Smith, a whaleboat man who filled in for Brewster near the end of the war, and William T. Robinson, a merchant.
Alexander Rose wrote that John Cork was a code name for an unidentified informant. Harry Thayer Mahoney wrote that John Corke of Groton, New York posed as a Tory and could travel back and forth to New York City because he was "exceedingly intimate at British headquarters." Corke wrote intelligence reports to Tallmadge in invisible ink or reported verbally to him. Mahoney states that Washington and Tallmadge considered Corke a valuable recruit for the Culper Ring. A letter by loyalist soldier Nehemia Marks uncovered in 2015 identified brothers Nathaniel and Phillip Roe as supporters of the spy ring, with Nathaniel providing intelligence and Phillip material aid. The letter also provides evidence that the Culper ring operated in Drowned Meadow beyond Setauket and Oyster Bay as previously believed. The letter is housed in the William L. Clements library at the University of Michigan where it was discovered by a former resident of Port Jefferson researching the Culper Ring.
Women in the Ring
Women, including Agent 355, whose identity remains unknown; Anna Strong; Robert Townsend's sister Sally Townsend; and Abraham Woodhull's sister Mary Underhill, who according to some sources provided important information about Major John Andre and his alias of John Anderson were informants for or participants in the Culper Ring.
Twentieth Century disclosure of the Ring
The general public was unaware of the Ring's existence until the 1930s. Robert Townsend's identity as "Culper, Jr.," was discovered in 1929, with the examination of old letters written by Townsend in the Townsend family home. Historian Morton Pennypacker reviewed the letters and noticed the resemblance of the handwriting in letters from the trunk written by Robert Townsend and letters written by "Samuel Culper, Jr.," in George Washington's collection. Other evidence later corroborated Townsend's identity. James Rivington was confirmed by scholars to be a member of the ring only in the 1950s.
In popular culture
- The Ubisoft Montreal video game Assassins Creed III (2012) includes an entry for the Culper Ring and Agent 355 in its in-game database of facts.
- The Firaxis PC game Civilization: Beyond Earth includes a National Wonder called a "Culper Lodge" that is created after successfully completing a quest involving covert operations.
- James Fenimore Cooper's novel The Spy (1821) may have been based on the Culper Ring, and Woodhull and Townsend (as the combined Samuel Culper) specifically
- Brian Kilmeade book George Washington's Secret Six (2013) is about the Culper Ring.
- Bruce Lancaster's novel The Secret Road (1952)
- Brad Meltzer's novel The Inner Circle (2011) and its sequels, The Fifth Assassin (2013) and The President's Shadow (2015) center on protagonist Beecher White, a member of a modern-day Culper Ring
- The Vertigo comic book series Y: The Last Man (2002) featured a modern Culper agent identified as "355"
- Roseanna M. White's Culper Ring series of novels, Ring of Secrets, Whispers from the Shadows, and Circle of Spies, feature the historical Culper Ring in book 1 and continues with conjecture on possible later actions in later books.
- The 2014 AMC television show Turn: Washington's Spies, based on Alexander Rose's history book Washington's Spies: The Story of America's First Spy Ring (2007), tells a fictionalized version of the story of the Culper Ring, with a focus on Abe Woodhull
- In season 4, episode 6 of White Collar, "Identity Crisis" (2012), the Culper Ring remains active in modern-day New York City, populated by descendants of its original members.
- In season 2, episode 10 of Sleepy Hollow, "Magnum Opus" (2014), Ichabod Crane dismisses the Parson Weems account of George Washington's honesty, pointing out that Washington's ties to the Culper Ring, whose agents engaged in deception, made him the revolution's "Liar-in-Chief."
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- Kilmeade, 2013, pp.93–94, doubts the laundry signals took place. Naylor, 2012, p. 38 attributes the story to oral folklore.
- Welch, Richard F. General Washington's Commando: Benjamin Tallmadge in the Revolutionary War. Jefferson, NC: McFarland & Company, Inc., 2014. ISBN 978-0-7864-7963-4. p. 37.
- Rose, 2007, p. 103.
- Rose, 2007, p. 106.
- Rose, 2007, p. 113.
- Rose, 2007, p. 129.
- Rose, 2007, p. 112.
- Rose, 2007, p. 112.
- Rose, 2007, p. 131.
- Rose, 2007, p. 132.
- Nelson, David Paul. Robert Townsend in Hastedt, Glenn, P., ed. Spies, Wiretaps, and Secret Operations: A-J. Santa Barbara, CA: ABC-CLIO, 2011. ISBN 978-1-85109-807-1. p. 763.
- Rose, 2007, pp. 150–154.
- Baker, Mark Allen. Spies of Revolutionary Connecticut: From Benedict Arnold to Nathan Hale. Charleston, SC: The History Press, 2014. ISBN 978-1-62619-407-6. p. 124
- Brady, Kevin M. Culper Spy Ring In Frank, Lisa Tendrich. An Encyclopedia of American Women at War: From the Home Front to the Battlefields. Santa Barbara, CA: ABC-CLIO, 2013. ISBN 978-1-59884-444-3. p. 172.
- Rose, 2007, p. 172.
- Kahn, David. The Codebreakers: The Comprehensive History of Secret Communication from Ancient Times to the Internet. New York, Simon and Schuster, 1996. ISBN 978-1-4391-0355-5. p. 179.
- Kilmeade says that Hawkins destroyed Culper letters on two occasions for fear of being caught. Kilmeade, 2013, p. 100.
- Kilmeade, 2013, P. 100.
- Rose, 2007, pp. 106–110.
- Rose, 2007, p. 121.
- Rose, 2007, p. 173 identifies Agent 355 as Anna Strong, but notes on p. 277 that she died in 1812, which is inconsistent with other accounts of 355's fate. Kilmeade, 2013, pp. 93–94 doubts that Anna Strong was Agent 355. He believes she was more likely to have been a younger woman living with a Loyalist family in New York and acquainted with British spy Major John André. Mahoney, 1999, p. 304, agrees that Agent 355 had access to British headquarters but identifies her as the mistress and common law wife of Robert Townsend, who died in childbirth in 1780 while confined on a British prison ship.
- Rose, 2007, pp. 224–226.
- Mahoney, 1999, p. 253.
- Bakeless, John. Turncoats, Traitors & Heroes. New York: Da Capo Press, 1998. Originally published New York: J. B. Lippincott, 1959. ISBN 978-0-306-80843-2. p. 240.
- Rose, 2007, p. 226.
- Rose, 2007, p. 224.
- Rose, 2007, p. 225.
- Knott, Stephen. Secret and Sanctioned: Covert Operations and the American Presidency. New York: Oxford University Press, 1996. ISBN 978-0-19-510098-3. Retrieved May 22, 2014. p. 40.
- Misencik, Paul R. The Original American Spies: Seven Covert Agents of the Revolutionary War. Jefferson, NC: McFarland, 2013. ISBN 978-0-7864-7794-4. p. 116.
- Misencik, 2013, p. 117.
- Misencik, 2013, p. 122.
- Mahoney, 1999, pp. 284–285, 308
- Rose, 2007, pp. 173, 255–256, 265.
- Rose, 2007, p. 255.
- Mahoney, 1999, p. 111.
- Leuzzi, Linda "A letter of Significance” Long Island Advance, October 22, 2015
- William L. Clements Library "The Sir Henry Clinton Collection" retrieved October 27, 2015
- Weigold, Marilyn E. (2004). The Long Island Sound: A History of Its People, Places, and Environment. New York: NYU Press. ISBN 978-0-8147-9400-5. Author Marilyn Weigold says the story about Sally Townsend providing this intelligence has been "deemed apocryphal," without giving a citation in the text.
- Kilmeade, 2013, pp. xvi–xvii.
- Mahl, Tom E. Espionage's Most Wanted: The Top 10 Book of Malicious Moles, Blown Covers, and Intelligence Oddities. Potomac Books, Inc., 2003. ISBN 978-1-61234-038-8. Retrieved May 1, 2014. p. 43.
- Walker, Warren S. "The Prototype of Harvey Birch". Retrieved April 27, 2014.
- Kilmeade, Brian (2013). George Washington's Secret Six.
- White, Roseanna M. "The Culper Ring Series". RoseannaWhite.com.
- Bakeless, John. Turncoats, Traitors & Heroes. New York: Da Capo Press, 1998. Originally published New York: J. B. Lippincott, 1959. ISBN 978-0-306-80843-2.
- Baker, Mark Allen. Spies of Revolutionary Connecticut: From Benedict Arnold to Nathan Hale. Charleston, SC: The History Press, 2014. ISBN 978-1-62619-407-6.
- Brady, Kevin M. Culper Spy Ring In Frank, Lisa Tendrich. An Encyclopedia of American Women at War: From the Home Front to the Battlefields. Santa Barbara, CA: ABC-CLIO, 2013. ISBN 978-1-59884-444-3. p. 172.
- Ferling, John. Almost a Miracle: The American Victory in the War of Independence. New York: Oxford University Press, 2009. ISBN 978-0-19-538292-1. (pbk.) Originally published in hard cover in 2007.
- Jones, Robert Francis. "The King of the Alley": William Duer, Politician, Entrepreneur, and Speculator, 1768-1799. Philadelphia: American Philosophical Society, 1992. ISBN 0-87169-202-3.
- Kahn, David. The Codebreakers: The Comprehensive History of Secret Communication from Ancient Times to the Internet. New York, Simon and Schuster, 1996. ISBN 978-1-4391-0355-5.
- Kilmeade, Brian and Don Yaeger. George Washington's Secret Six: The Spy Ring That Save the American Revolution. New York: Penguin Group, 2013. ISBN 978-1-59523-103-1.
- Knott, Stephen. Secret and Sanctioned: Covert Operations and the American Presidency. New York: Oxford University Press, 1996. ISBN 978-0-19-510098-3. Retrieved May 22, 2014.
- Leckie, Robert. George Washington's War: The Saga of the American Revolution. New York: Harper Perennial, a division of HarperCollins, 1993. ISBN 978-0-06-092215-3. First published 1992.
- Macmillan, Margaret Burnham. The War Governors in the American Revolution. New York: Columbia University Press, 1943. OCLC 3093783. Retrieved April 22, 2014. – via Questia (subscription required)
- Mahl, Tom E. Espionage's Most Wanted: The Top 10 Book of Malicious Moles, Blown Covers, and Intelligence Oddities. Potomac Books, Inc., 2003. ISBN 978-1-61234-038-8. Retrieved May 1, 2014.
- Mahoney, Henry Thayer and Marjorie Locke Mahoney. Gallantry in Action: A Biographic Dictionary of Espionage in the American Revolutionary War. Lanham, MD: University Press of America, Inc., 1999. ISBN 978-0-7618-1479-5.
- Misencik, Paul R. The Original American Spies: Seven Covert Agents of the Revolutionary War. Jefferson, NC: McFarland, 2013. ISBN 978-0-7864-7794-4. p. 122.
- Naylor, Natalie A. Women in Long Island's Past: A History of Eminent Ladies and Everyday Lives. Charleston, SC: The History Press, 2012. ISBN 978-1-60949-499-5. Retrieved May 1, 2014.
- Nelson, David Paul. Culper Ring in Hastedt, Glenn, P., ed. Spies, Wiretaps, and Secret Operations: A-J. Santa Barbara, CA: ABC-CLIO, 2011. ISBN 978-1-85109-807-1.
- Rose, Alexander. The Spy Who Never Was: The Strange Case of John Honeyman and Revolutionary War Espionage. In CIA Studies in Intelligence Journal, June 19, 2008. Retrieved May 30, 2014.
- Rose, Alexander. Washington's Spies: The Story of America's First Spy Ring. New York: Bantam Dell, a division of Random House, 2007. First published in hardcover in 2006. ISBN 978-0-553-38329-4.
- Schellhammer, Michael. George Washington and the Final British Campaign for the Hudson River, 1779. Jefferson, NC: McFarland and Co., Inc., 2012. ISBN 0786468076.
- Sharp, Arthur G. Not Your Father's Founders: An "Amended" Look at America's First Patriots. Avon, MA: Adams Media, 2012. ISBN 978-1-4405-4011-0.
- Tallmadge, Benjamin. Memoir of Col. Benjamin Tallmadge. New York: Thomas Holman, 1858. OCLC 15547874.
- Ward, Christopher. John Richard Alden, ed. The War of the Revolution. New York: Skyhorse Publishing, 2011. ISBN 978-1-61608-080-8. Originally published Old Saybrook, CT: Konecky & Konecky, 1952.
- Weigold, Marilyn E. The Long Island Sound: A History of Its People, Places, and Environment. New York: NYU Press, 2004. ISBN 978-0-8147-9400-5.
- Washington's Spies by Alexander Rose book talk at C-SPANvideo.org
- Long Island's Spy Chain
- The Culper Spy Ring
- Spy Networks: The Culper Gang
- Three Village Historical Society Setauket Spy Ring Web Article
- Caleb Brewster letter correspondence including with George Washington