The river looking north above Walpack Bend, where it leaves the historic Minisink region, a buried valley eroded from Marcellus Shale bedrock.
|States||New York, New Jersey, Pennsylvania, Delaware|
|- left||Neversink River, Musconetcong River|
|- right||Lehigh River, Schuylkill River|
|Cities||Port Jervis, NY, Easton, PA, Trenton, NJ, Camden, NJ, Philadelphia, PA, Wilmington, DE|
|- location||Mount Jefferson, Town of Jefferson, Schoharie County, New York, United States|
|- elevation||2,240 ft (683 m)|
|Secondary source||East Branch|
|- location||Grand Gorge, Town of Roxbury, Delaware County, New York, United States|
|- elevation||1,560 ft (475 m)|
|- elevation||880 ft (268 m)|
|- elevation||0 ft (0 m)|
|Length||301 mi (484 km)|
|Basin||14,119 sq mi (36,568 km2)|
|- average||13,100 cu ft/s (371 m3/s)|
|- max||329,000 cu ft/s (9,316 m3/s)|
|- min||4,310 cu ft/s (122 m3/s)|
|Discharge elsewhere (average)|
|- Port Jervis||7,900 cu ft/s (224 m3/s)|
The Delaware River is a major river on the Atlantic coast of the United States. Its watershed drains an area of 14,119 square miles (36,570 km2) in five U.S. states—New York, New Jersey, Pennsylvania, Maryland and Delaware. Rising in two branches in New York state's Catskill Mountains, the river flows 419 miles (674 km) into Delaware Bay where its waters enter the Atlantic Ocean near Cape May in New Jersey and Cape Henlopen in Delaware. Not including Delaware Bay, the river's length including its two branches is 388 miles (624 km). The Delaware River is one of nineteen "Great Waters" recognized by the America's Great Waters Coalition.
The Delaware River rises in two main branches that descend from the western flank of the Catskill Mountains in New York. The West Branch begins near Mount Jefferson in the Town of Jefferson in Schoharie County. The river's East Branch begins at Grand Gorge near Roxbury Delaware County. These two branches flow west and merge near Hancock in Delaware County and the combined waters flow as the Delaware River south. Through its course, the Delaware River forms the boundaries between Pennsylvania and New York, the entire boundary between New Jersey and Pennsylvania, and most of the boundary between Delaware and New Jersey. The river meets tide-water at Trenton, New Jersey (once called "Falls of the Delaware") and the river's navigable and tidal section served as a conduit for shipping and transportation that aided the development of the industrial cities of Trenton, Camden and Philadelphia. The mean freshwater discharge of the Delaware River into the estuary of Delaware Bay is 11,550 cubic feet (330 m³) per second.
In 1609, the river was first visited by a Dutch East India Company expedition led by Henry Hudson. Hudson, an English navigator, was hired to find a western route to Cathay (present-day China), but his discoveries set the stage for Dutch colonization of North America in the seventeenth-century. Early Dutch and Swedish settlements were established along the lower section of river and Delaware Bay. Both colonial powers called the river the South River compared to the Hudson River which was known as the North River. After the English expelled the Dutch and took control of the New Netherland colony in 1664, the river was renamed Delaware after Sir Thomas West 3rd Baron De La Warr, an English nobleman and the Virginia colony's first royal governor who defended the colony during the First Anglo-Powhatan War.
West Branch of the Delaware 
The West or Mohawk branch rises in Schoharie County, New York, about 1,886 feet (575 m) above sea level, near Mount Jefferson, and flows tortuously through the plateau in a deep trough, impounded at one point to create the Cannonsville Reservoir, and then becoming the state boundary of New York and Pennsylvania at the 42nd parallel, until it emerges from the Catskills.
East Branch of the Delaware 
Similarly, the East Branch begins from a small pond south of Grand Gorge in the town of Roxbury in Delaware County, flowing southwest toward its impoundment by New York City to create the Pepacton Reservoir, the largest reservoir in the New York City water supply system. Its tributaries are the Beaver Kill River and the Willowemoc Creek which enter into the river ten miles (16 km) before the West Branch meets the East Branch. The confluence of the two branches is just south of Hancock.
Both the East Branch and West Branch of the Delaware River parallel each other, both flowing in a southwesterly direction.
Upper Delaware Valley 
From Hancock, the river flows between The Poconos and the lowered shale beds north of the Catskills. The river flows down a broad Appalachian valley, passing Hawk's Nest overlook on the Upper Delaware Scenic Byway.
The Minisink 
At Port Jervis, New York, it enters the Port Jervis trough. At this point, the Walpack Ridge deflects the Delaware into the Minisink Valley, where it follows the southwest strike of the eroded Marcellus Formation beds along the Pennsylvania–New Jersey state line for 25 miles (40 km) to the end of the ridge at Walpack Bend in the Delaware Water Gap National Recreation Area. The Minisink is a buried valley where the Delaware flows in a bed of glacial till that buried the eroded bedrock during the last glacial period. It then skirts the Kittatinny ridge, which it crosses at the Delaware Water Gap, between nearly vertical walls of sandstone, quartzite, and conglomerate, and then passes through a quiet and charming country of farm and forest, diversified with plateaus and escarpments, until it crosses the Appalachian plain and enters the hills again at Easton, Pennsylvania. From this point it is flanked at intervals by fine hills, and in places by cliffs, of which the finest are the Nockamixon Rocks, 3 miles (5 km) long and above 200 feet (61 m) high.
Central Delaware Valley 
The Lower Delaware and Tide-Water 
Below Trenton the river flows between Philadelphia and New Jersey before becoming a broad, sluggish inlet of the sea, with many marshes along its side, widening steadily into its great estuary, Delaware Bay.
The Delaware River constitutes part of the boundary The Delaware-New Jersey border is actually at the easternmost river shoreline within the Twelve-Mile Circle of New Castle, rather than mid-river or mid-channel borders, causing small portions of land lying west of the shoreline, but on the New Jersey side of the river, to fall under the jurisdiction of Delaware. The rest of the borders follow a mid-channel approach.
Tributaries and watershed 
The Delaware River's watershed drains an area of 14,119 square miles (36,570 km2) in four U.S. states—New York, New Jersey, Pennsylvania and Delaware.
The main tributaries in New York are the Mongaup and Neversink rivers and Callicoon Creek. From Pennsylvania, the major tributaries are the Lackawaxen, Lehigh, and Schuylkill rivers. From New Jersey, the Big Flatbrook, Pequest, Musconetcong, and Maurice rivers, plus Oldmans, Raccoon and Rancocas creeks, flow into the Delaware.
The Delaware River played a key factor in the economic and social development of the Mid-Atlantic region. In the seventeenth century is provided the conduit for colonial settlement by the Dutch (New Netherland), the Swedish (New Sweden). Beginning in 1664, the region became an English possession as settlement by Quakers established the colonies of Pennsylvania (including present-day Delaware) and West Jersey. In the eighteenth century, cities like Philadelphia, Camden (then Cooper's Ferry), Trenton, and Wilmington, New Castle, New Castle were established upon the Delaware and their continued commercial success into the present day has been dependent on access to the river for trade and power. The river provided the path for the settlement of northeastern Pennsylvania's Lehigh Valley, and northwestern New Jersey by German Palatine immigrants—a population that became key in the agricultural development of the region.
Washington's crossing of the Delaware 
Perhaps the most famous “Delaware Crossing” involved the improvised boat crossing undertaken by George Washington’s army during the American Revolution on the night of December 25–26, 1776. This led to a successful surprise attack on the Hessian troops occupying Trenton, New Jersey.
The magnitude of the commerce of Philadelphia has made the improvements of the river below that port of great importance. Small improvements were attempted by Pennsylvania as early as 1771. Commerce was once important on the upper river, primarily prior to railway competition (1857).
- The Delaware Division of the Pennsylvania Canal, running parallel with the river from Easton to Bristol, opened in 1830.
- The Delaware and Raritan Canal, which runs along the New Jersey side of the Delaware River from Bulls Island, New Jersey to Trenton, unites the waters of the Delaware and Raritan rivers as it empties the waters of the Delaware River via the canal outlet in New Brunswick. This canal water conduit is still used as a water supply source by the State of New Jersey.
- The Morris Canal (now abandoned and almost completely filled in) and the Delaware and Hudson Canal connected the Delaware and Hudson rivers.
- The Chesapeake and Delaware Canal joins the waters of the Delaware with those of the Chesapeake Bay.
In the "project of 1885" the U.S. government undertook systematically the formation of a 26-foot (7.9 m) channel 600 feet (180 m) wide from Philadelphia to deep water in Delaware Bay. The River and Harbor Act of 1899 provided for a 30-foot (9.1 m) channel 600 feet (180 m) wide from Philadelphia to the deep water of the bay.
Delaware Water Gap National Recreation Area 
The Delaware Water Gap National Recreation Area came about as a result of the failure of a controversial plan to build a dam on the Delaware River at Tocks Island, just north of the Delaware Water Gap to control water levels for flood control and hydroelectric power generation. The dam would have created a 37-mile (60 km) lake in the center of present park for use as a reservoir. Starting in 1960, the present day area of the Recreation Area was acquired for the Army Corps of Engineers through eminent domain. Between 3,000 and 5,000 dwellings were demolished, including historical sites, and about 15,000 people were displaced by the project.
Because of massive environmental opposition, dwindling funds, and an unacceptable geological assessment of the dam's safety, the government transferred the property to the National Park Service in 1978. The National Park Service found itself as the caretaker of the previously endangered territory, and with the help of the federal government and surrounding communities, developed recreational facilities and worked to preserve the remaining historical structures.
Ports and trade 
Bridge crossings 
The Delaware River is a major barrier to travel between New Jersey and Pennsylvania. Most of the larger bridges are tolled only westbound, and are owned by the Delaware River and Bay Authority, Delaware River Port Authority, Burlington County Bridge Commission or Delaware River Joint Toll Bridge Commission.
Environmental issues 
New York City water supply 
After New York City had built 15 reservoirs to supply water to the city's growing population, it was unable to obtain permission to build an additional five reservoirs along the Delaware River's tributaries. As a result, in 1928 the city decided to draw water from the Delaware River, putting then in direct conflict with villages and towns across the river in Pennsylvania which were already using the Delaware for their water supply. The two sides eventually took their case to the U.S. Supreme Court, and in 1931, New York City was allowed to draw 440 million US gallons (1,700,000 m3) of water a day from the Delaware and its upstream tributaries.
With the failure of the dam project to come to fruition, the lack of flood control on the river left it vulnerable, and it has experienced a number of serious flooding events as the result of snow melt or rain run-off from heavy rainstorms. Record flooding occurred in August 1955, in the aftermath of the passing of the remnants of two separate hurricanes over the area within less than a week: first Hurricane Connie and then Hurricane Diane, which was, and still is, the wettest tropical cyclone to have hit the northeastern United States. The river gauge at Riegelsville, Pennsylvania recorded an all time record crest of 38.85 feet (11.84 m) on August 19, 1955.
More recently, moderate to severe flooding has occurred along the river. The same gauge at Riegelsville recorded a peak of 30.95 feet (9.43 m) on September 23, 2004, 34.07 feet (10.38 m) on April 4, 2005, and 33.62 feet (10.25 m) on June 28, 2006, all considerably higher than the flood stage of 22 feet (6.7 m).
Since the upper Delaware basin has few population centers along its banks, flooding in this area mainly affects natural unpopulated flood plains. Residents in the middle part of the Delaware basin experience flooding, including three major floods in the three years (2004–2006) that have severely damaged their homes and land. The lower part of the Delaware basin from Philadelphia southward to the Delaware Bay is tidal and much wider than portions further north, and is not prone to river related flooding (although tidal surges can cause minor flooding in this area).
The Delaware River Basin Commission, along with local governments, is working to try to address the issue of flooding along the river. As the past few years have seen a rise in catastrophic floods, most residents of the river basin feel that something must be done. The local governments have worked in association with FEMA to address many of these problems, however, due to insufficient federal funds, progress is slow.
Major oil spills 
- 01-31-1975 — around 11,172,000 US gallons (42,290 m3) of crude oil spilled from the Corinthos tanker
- 09-28-1985 — 435,000 US gallons (1,650 m3) of crude oil spilled from the Grand Eagle tanker after running aground on Marcus Hook Bar
- 06-24-1989 — 306,000 US gallons (1,160 m3) of crude oil spilled from the Presidente Rivera tanker after running aground on Claymont Shoal
- 11-26-2004 — 265,000 US gallons (1,000 m3) of crude oil spilled from the Athos 1 tanker; the tanker's hull had been punctured by a submerged, discarded anchor
See also 
- Foul Rift, rapids just south of Belvidere, New Jersey
- Geography of Pennsylvania
- List of crossings of the Delaware River
- List of Delaware rivers
- List of New Jersey rivers
- List of New York rivers
- List of Pennsylvania rivers
- Partnership for the Delaware Estuary
- Tocks Island
- Upper Delaware Scenic and Recreational River
- Washington Crossing (disambiguation)
- The main stem from Hancock, New York to the head of Delaware Bay is 301 miles (484 km).
- U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National Map, accessed April 1, 2011
- National Wildlife Federation (August 18, 2010). "America's Great Waters Coalition". Retrieved 2011-18-20.
- White, Ron W.; Monteverde, Donald H. (02-01-2006). "Karst in the Delaware Water Gap National Recreation Area" (pdf). Unearthing New Jersey Vol. 2, No. 1. New Jersey Geological Survey. Retrieved 06-07-2008.
- White, I.C.; Chance, H.M. (1882). The geology of Pike and Monroe counties. Second Geol. Surv. of Penna. Rept. of Progress, G6. Harrisburg. pp. 17, 73–80, 114–115.
- Delaware Water Gap National Recreation Area (p. 7-8), Obiso, Laura, 2008.
- Delaware Water Gap National Recreation Area, njskylands.com.
- USGS See Also: (State of New Jersey: Recent flooding events in the Delaware river basin
- Delaware River Basin Commission (2005-07-20). "Delaware River Basin Commission’s Role in Flood Loss Reduction Efforts." West Trenton, NJ.
- "Athos 1 Oil Spill". University of Delaware Sea Grant Program. 03-11-2005. Retrieved April 29, 2006.
- "1985 Grand Eagle Oil Spill". University of Delaware Sea Grant Program. 12-16-2004. Retrieved April 29, 2006.
- "Presidente Rivera Spill – June 24, 1989". University of Delaware Sea Grant Program. 2004-12-08. Retrieved April 29, 2006.
- This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Delaware River". Encyclopædia Britannica (11th ed.). Cambridge University Press.
- Devastation on the Delaware: Stories and Images of the Deadly Flood of 1955 (2005, Word Forge Books, Ferndale, PA) The only comprehensive documentary of this weather disaster in the Delaware River Valley.
|Wikimedia Commons has media related to: Delaware River|
|Wikisource has the text of a 1921 Collier's Encyclopedia article about Delaware River.|
- Delaware Riverkeeper Network
- National Park Service: Delaware Water Gap National Recreation Area
- National Park Service: Upper Delaware Scenic & Recreational River
- National Park Service: Lower Delaware Wild & Scenic River
- U.S. Geological Survey: NJ stream gaging stations
- U.S. Geological Survey: NY stream gaging stations
- U.S. Geological Survey: PA stream gaging stations
- Marine Railway and Sectional Floating Dry Dock, Delaware River, Philadelphia, 1893 by D.J. Kennedy, Historical Society of Pennsylvania
- Winter on the River Delaware, 1856. Shows "U.S.S. Prowhatan" by D.J. Kennedy, HSP
- "Map of the South River in New Netherland" from ca. 1639 via the World Digital Library