the Grants. When the American Revolutionary War broke out, Allen and the Boys seized Fort Ticonderoga in May 1775. In September 1775 Allen led a failed attempt on Montreal that resulted in his capture by British authorities. First imprisoned aboard Royal Navy ships, he was paroled in New York City, and finally released in a prisoner exchange in 1778.
Upon his release, Allen was active in efforts by Vermont's leadership for recognition by Congress, and he participated in controversial negotiations with the British over the possibility of Vermont becoming a separate British province. Allen wrote accounts of his exploits in the war that were widely read in the 19th century, as well as philosophical treatises and documents relating to the politics of Vermont's formation. His business dealings included successful farming operations, one of Connecticut's early iron works, and land speculation in the Vermont territory. Land purchased by Allen and his brothers included tracts of land that eventually became Burlington, Vermont. He was twice married, fathering eight children.