William Penn signs a friendship treaty with Lenni Lenape Indians in Pennsylvania.

William Penn (14 October 1644 – 30 July 1718) was an English writer and religious thinker belonging to the Religious Society of Friends (Quakers), and founder of the Province of Pennsylvania, a North American colony of England. He was an early advocate of democracy and religious freedom, notable for his good relations and successful treaties with the Lenape Native Americans.

In 1681, King Charles II handed over a large piece of his North American land holdings along the North Atlantic Ocean coast to Penn to pay the debts the king had owed to Penn's father, the admiral and politician Sir William Penn. This land included the present-day states of Pennsylvania and Delaware. Penn immediately set sail and took his first step on American soil, sailing up the Delaware Bay and Delaware River, (past earlier Swedish and Dutch riverfront colonies) in New Castle (now in Delaware) in 1682. On this occasion, the colonists pledged allegiance to Penn as their new proprietor, and the first Pennsylvania General Assembly was held. Afterward, Penn journeyed further north up the Delaware River and founded Philadelphia, on the west bank. However, Penn's Quaker government was not viewed favorably by the previous Dutch and Swedish colonists, and earlier English settlers in what is now Delaware, but claimed for half a century by the neighboring Province of Maryland's proprietor family, the Calverts and Lord Baltimore. These earlier colonists had no historical allegiance to a "Pennsylvania", so they almost immediately began petitioning for their own representative assembly. Twenty-three years later in 1704, they achieved their goal when the three southernmost counties of provincial Pennsylvania along the western coast of the Delaware were permitted to split off and become the new semi-autonomous colony of Lower Delaware. As the most prominent, prosperous and influential settlement in the new colony, New Castle, the original Swedish colony town became the capital.

As one of the earlier supporters of colonial unification, Penn wrote and urged for a union of all the English colonies in what was to become the United States of America. The democratic principles that he set forth in the Pennsylvania Frame of Government served as an inspiration for the members of the convention framing the new Constitution of the United States in Philadelphia in 1787.As a pacifist Quaker, Penn considered the problems of war and peace deeply. He developed a forward-looking project and thoughts for a "United States of Europe" through the creation of a European Assembly made of deputies who could discuss and adjudicate controversies peacefully. He is therefore considered the first thinker to suggest the creation of a European Parliament and what would become the modern European Union in the late 20th century.A man of deep religious convictions, Penn wrote numerous works in which he exhorted believers to adhere to the spirit of Primitive Christianity. He was imprisoned several times in the Tower of London due to his faith, and his book No Cross, No Crown (1669), which he wrote while in prison, has become a Christian classic of theological literature.