American Revolution
The Penns were slow to perceive that the growing unrest, which became the American Revolution, would threaten their proprietary interests. In 1774, Penn refused to summon the Assembly so it could select delegates to the First Continental Congress. Patriots responded by taking control in 1775, leaving Penn powerless. Henry J. Cadbury states, "The end of proprietary government in Pennsylvania may be dated Sept. 26, 1776, with the last adjournment of the provincial assembly. The governor's acts and meetings of the council closed nearly a year earlier."
After the American Revolutionary War was launched at the Battles of Lexington and Concord, Penn watched with apprehension as Pennsylvania colonists formed patriot militias and prepared for war. Soon after the adoption of the Declaration of Independence, patriots, also known as Whigs, in Pennsylvania created the Pennsylvania Constitution of 1776, which replaced Penn's government with a Supreme Executive Council and no royal officials. With no power at his command, Penn remained aloof and carefully neutral in the hope that the radicals would be defeated or at least reconciled with the king.
The war soon began to go badly for the Patriots. In August 1777, as General William Howe began his Philadelphia Campaign, Patriot soldiers arrived at Penn's Lansdowne estate near Philadelphia. They demanded him to sign a parole that stated that he would do nothing to harm the revolutionary cause. Penn refused and was taken to Philadelphia, where he was kept under house arrest. As Howe's army drew close, the Patriots threatened Penn with exile to another colony, and he then signed the parole. With Howe near Philadelphia, Patriot leaders exiled Penn to an Allen family estate in New Jersey called "The Union," also known as Solitude House, about 50 miles (80 km) from Philadelphia in present-day High Bridge, New Jersey.
Anne Penn initially stayed in Philadelphia to look after family affairs while British forces occupied Philadelphia but later joined her husband in New Jersey.
After the British evacuated Philadelphia in 1778, the Penns returned to the city in July of that year. The new government of Pennsylvania required all residents to take a loyalty oath to the Commonwealth or to face confiscation of their property. With the consent of his family, he took the oath. While that protected Penn's private lands and manors, the Pennsylvania Assembly passed the Divestment Act of 1779, which confiscated about 24,000,000 acres (97,000 km2) of unsold lands held by the proprietorship and abolished the practice of paying quitrents for new purchases. As compensation, John Penn and his cousin were paid £130,000, but that was a fraction of what the lands were worth but was a surprisingly large sum, as in some areas, Loyalist properties were taken without any compensation. Penn retired to Lansdowne and waited out the final years of the war, which ended in 1781.