Margaret Mattson and her husband Neals Mattson lived on a farm near Ridley Creek in present-day Eddystone, Pennsylvania. Part of Eddystone township at the mouth of Ridley Creek, had been taken up by Olof Persson Stille, one of the early settlers of the Swedish colony of New Sweden who had arrived during 1641. One hundred acres of the Stille land was patented to Neals Mattson on June 13, 1670. Mattson's choice for their plantation was rich, fertile river land by the Delaware River.
Of Swedish-Finnish descent, Neals and Margaret Mattson were also likely members of the former New Sweden colony which occupied much of the lower Delaware River Valley from 1638 to 1655. Mattson was a reputed healer working from Finnish tradition. After New Sweden was taken over by the British, some of her neighbors claimed that she had bewitched cattle.
Charges of practicing witchcraft were brought before the Pennsylvania Provincial Council on February 7, 1683 (under Julian calendar). This occurred one and a half years after William Penn arrived on October 27, 1682, on the vessel Welcome and landed to take seisin possession of Pennsylvania, his royal land grant colony of "Penn's Woods" named after his father by King Charles II. Pennsylvania was a common law colony and the law of England applied. The English Witchcraft Act of 1604 made conjuration, witchcraft, and dealing with evil and wicked spirits a felony offense punishable by death by hanging without benefit of clergy. Like other British colonies, Pennsylvania was subject to the James I of England 1604 statute against witchcraft; however, Mattson's and Hendrickson's is the only such trial recorded from the Pennsylvania Colony.
Accused by several neighbors, as well as her own daughter, Mattson's alleged crimes included making threats against neighbors, causing cows to give little milk, bewitching and killing livestock and appearing to witnesses in spectral form. On February 27, 1683, charges against Mattson and a neighbor Gertro (a.k.a. Yeshro) Hendrickson were brought by the Attorney General before a grand jury of 21 men overseen by the colony's proprietor, William Penn. The grand jury returned a true bill indictment that afternoon, and the cases proceeded to trial. A petit jury of 12 men was selected by Penn and an interpreter was appointed for the Swedish women, who did not speak English. Penn barred the use of prosecution and defense lawyers, conducted the questioning himself, and permitted the introduction of unsubstantiated hearsay. Penn himself gave the closing charge and directions to the jury, but what he told them was not transcribed. According to the minutes of the Provincial Council, dated February 27, 1683, the jury returned with a verdict of "Guilty of having the Comon Fame of a Witch, but not Guilty in manner and Forme as Shee stands Endicted."
Thus Mattson was found guilty of having the reputation of a witch, but not guilty of bewitching animals. Neither woman was convicted of witchcraft. "Hence the superstitious got enough to have their thinking affirmed. Those less superstitious, and justice minded, got what they wanted." The accused were released on their husbands posting recognizance bonds of 50 pounds and promising six months' good behavior.
A popular legend tells of William Penn dismissing the charges against Mattson by affirming her legal right to fly on a broomstick, saying "Well, I know of no law against it." The record fails to show any such commentary, but the story probably reflects popular views of Penn's socially progressive Quaker values.
- Witchcraft and Quakerism: A Study in Social History (Chapter IV, by Amelia Mott Gummere. Street Corner Society) 
- History of Ridley Township, Pa. (from: A History of Delaware County, Pennsylvania. John W. Jordan, Published By Lewis Historical Publishing Company, New York 1914) 
- Pennsylvania’s Only Witch Trial (from: Quakers in the World. Ideas for Educators) 
- Some of The Famous Witch Trials In Pennsylvania (The Realness of Witchcraft In America. Northvegr Foundation) 
- "The Fame Of A Witch" (The Pennsylvania Lawyer. Craig R. Shagin, Published by the Pennsylvania Bar Association, September-October 2016) 
- Statutes of the Realm (London 1817; repr. The Statutes, 3rd ed., London, 1950) 
- Before Salem, a witch inquiry in Pennsylvania - The case offered William Penn a chance to show his tolerance Joseph S. Kennedy, Philadelphia Inquirer, August 1, 2004
- Minutes of the Provincial Council of Pennsylvania..., vol. 1, J. Severns, Philadelphia: PA Provincial Council, 1852, pp. 95-96.
- PA History Witch -- Margaret Mattson was Profiled and Arrested in the 1680's, (by Tom Roy Smith, AKA The Ghost of William Penn. Delaware County Daily Times, October 15, 2013) 
- The Century Magazine, (by J. M. Buckley. December 1891 Vol. XLIII, No. 2) 
- Weird Pennsylvania. (by Matt Lake. New York: Sterling Publishers. 2005)
- Jordan, John W. A History of Delaware County, Pennsylvania. (Lewis Historical Publishing Company, New York. 1914)
- Benson, Adolph B. and Naboth Hedin, eds. Swedes in America, 1638-1938 (The Swedish American Tercentenary Association. New Haven, CT: Yale University Press. 1938) ISBN 978-0-8383-0326-9