Thomas McKean, born in New London, Pennsylvania, studied law, serving as the clerk of the Court of Common Pleas while still a student. Admitted to the bar in Delaware before he turned 21, he was appointed deputy Attorney General to county Sussex in Pennsylvania in 1756. He was elected a delegate to the Assembly in 1762 and re-elected for 17 years, serving as Speaker of the Assembly in 1772. He attended the Continental Congress from 1774, served on the committee to draw up the Articles of Confederation, and was commissioned a colonel in the New Jersey militia. In 1777, while serving in the Congress, he was appointed Chief Justice of Pennsylvania, holding the office for nearly 20 years. He was elected Governor of Pennsylvania in 1799 and filled that office by popular re-election for nine years before retiring in 1812, despite political enemies' unsuccessful attempt to impeach him. In 1787, he attended the ratifying convention for the new Federal Constitution and played a role in amending the constitution of Pennsylvania in 1789.
