With several hundred members, the Green Mountain Boys effectively controlled the area where New Hampshire grants had been issued. They were led by Ethan Allen, his brother Ira Allen, and their cousins Seth Warner and Remember Baker. They were based at the Catamount Tavern in Bennington, only a short distance from the New York seat of government in Albany. By the 1770s, the Green Mountain Boys had become an armed military force and de facto government that prevented the Albany government from exercising its authority in the northeast portion of the Province of New York. New York authorities had standing warrants for the arrests of the leaders of the rebellious Vermonters, but were unable to exercise them. New York surveyors and other officials attempting to exercise their authority were prevented from doing so and in some cases were severely beaten.
When the American Revolutionary War started in 1775, Ethan Allen and a force of his guerrillas, along with Massachusetts Colonel Benedict Arnold, marched up to Lake Champlain and captured the important military posts at Fort Ticonderoga, Fort Crown Point, Fort Ann, and the town of St. John (Battle of Fort St. Jean) in Québec. The Green Mountain Boys later formed the basis of the Vermont militia which selected Seth Warner as its leader. Some of the Green Mountain Boys preferred to stick with Ethan Allen and were captured along with Allen in August 1775 in a bungled attack on the city of Montreal. A member of this unit was Congressman Matthew Lyon.
Vermont eventually declared itself an independent nation in January 1777, and organized a government based in Windsor. The army of the Vermont Republic was based upon the Green Mountain Boys. Although Vermont initially supported the American Revolutionary War and sent troops to fight John Burgoyne's British invasion from Canada at Hubbardton and Bennington in 1777, Vermont eventually adopted a more neutral stance and became a haven for deserters from both the British and colonial armies. George Washington, who had more than sufficient difficulties with the British, brushed off Congressional demands that he subdue Vermont. The Vermont Army version of the Green Mountain Boys faded away after Vermont joined the United States as the 14th U.S. state in 1791. They returned for the War of 1812, the Civil War, and later more formally as the Vermont National Guard.