Born in the colony of Maryland, Carroll was educated abroad at the time of The Enlightenment. He returned to America shortly after the French and Indian War, finding the nation deeply divided over the policies of King George III. From this point forward he was an active participant in the movement towards liberty. When the Continental Congress was convened, Carroll was chosen, along with Benjamin Franklin and Samuel Chase, to go to Canada to encourage them to join the American colonies in relinquishing their allegiance to the British crown. The group was not successful.

He signed the Declaration of Independence on August 2, 1776, along with most of the delegates to the Continental Congress, and continued to serve in that august body until 1778.

Following his participation in national politics, he returned to his, married and was extremely active in the state political system. From the deaths of Thomas Jefferson and John Adams on July 4, 1826, Carroll was the only living signer of the Declaration, and was highly respected for this fact.