He was born in northern Ireland; his family emigrated to Cheshire County, Pennsylvania when he was about ten years old. He studied law at the office of his brother George and was admitted to the bar in Pennsylvania, initially practicing near Shippensburg, and later near York. He became captain of the militia there. He was appointed to the provincial convention in Philadelphia in 1775 and to the state constitutional convention in 1776 and was elected to the Continental Congress. He was reelected to Congress in 1785 but declined to attend because of his advanced age.