An active member of the colonial militia, Caswell was elected to the Continental Congress in 1774. He was promoted to brigadier general of the North Carolina militia in 1776, and served as chairman of a group to draft a state constitution, which was adopted, following the Declaration of Independence, by the Continental Congress. General Caswell was chosen and reelected Governor of North Carolina by the general assemblies of 1777, 1778 and 1779. Caswell was again elected N.C. Governor in 1785, 1786 and 1787, and died in 1789 while presiding over the state senate in the general assembly at Fayetteville.