It is believed that John Penn was born in either 1740 or 1741 on a prosperous farm in Caroline County, Virginia. He received little in the way of a formal education while growing up, but he later compensated for this deficiency through independent study. He was admitted to the bar after three years of legal study, and by 1774 he had a well-established and successful law practice.
It was around 1774 that Penn entered politics. He moved to Granvill County, North Carolina in this year, was elected to provincial assembly and then almost immediately after to the Continental Congress. He served on the Congress from 1775 to 1780. He became the leader of the North Carolina delegation in 1777, and was among sixteen signers of the Declaration of Independence who also signed the Articles of Confederation.
Penn was primarily devoted to his own law practice after leaving the Congress, except for the brief period time spent working as State tax receiver for the Confederation. He was only in his late forties when he died in 1788. His grave is in the Guilford Courthouse National Military Park, not far from Greensboro, North Carolina.