Settlers in what now is Vermont were caught between Benning Wentworth of New Hampshire and Gov. George Clinton of New York, disputing the territory in the mid-18th century. King George III ruled in favor of New York, and 135 grants were declared null and void. Settlers were shocked and angered, fearful of losing their lands. Violence against New York authority was common.

The Green Mountain Boys, under Ethan Allen, harassed holders of Vermont land with New York titles. As the only military group of the colony, they were able to support the American cause against the British, notably by helping Benedict Arnold capture the British fortress at Ticonderoga in 1775. With the signing of the Declaration of Independence, Vermont settlers considered their future. In 1777 Vermont adopted a constitution, nearly identical to that of Pennsylvania, and became the independent Republic of New Connecticut, alias Vermont. After 14 years as an independent republic, Vermont was admitted to the Union as the 14th state on March 4, 1791.