William Gilliland, for whom the town of Willsboro is named, began to settle land along Lake Champlain in 1765. He was a prosperous New York City merchant of Irish descent who planned to establish a baronial estate in the Champlain Valley. In the course of his explorations, he also discovered AuSable Chasm.
In Willsboro sits one of the earliest relics of the Adirondacks, the Adsit Cabin. Believed to have been built in 1779 by Samuel Adsit, it remained in the family until the 1900's. Open to the public during the summer, it has been restored to its original appearance.
By the end of the 18th century the lake towns of Westport, Willsboro, and Essex had developed rapidly. Platt Rogers had received a contract from the state and connected Westport and Willsboro by road. A mountain trail connected Willsboro to Bosworth's Tavern in Chesterfield.
The first ironworks were built in Willsboro in 1800 with the iron being shipped by boat to Albany. The early settlement contained a blacksmith, a hatter, a potash factory, a tavern, as well as school districts. "The Father of Churches in Essex County", Father Cyrus Comstock founded the Congregational church here as the century turned. During the Revolution, the mouth of the Boquet River was the site of General Burgoyne's campground. In the same location on May 13, 1814, a pivotal moment in the war occurred when the British attempted an attack up the Boquet. They were repulsed. Forty British were killed or wounded to every three colonials wounded.
Willsboro had a thriving quarry industry. Clark's Quarry, on the margin of Willsboro Bay was composed of two varieties of Trenton Limestone. In 1869, they employed nearly three hundred laborers and loaded a canal boat daily from their wharf. They had won a contract for supplying stone to be used in the construction of the new state capitol in Albany as well as the Brooklyn Bridge.
Industry collapsed here as it did elsewhere in the county, by the beginning of the 1900's. When the horsenail factory burned down in 1918, it was not rebuilt. The town is currently home to NYCO Minerals and Commonwealth Home Fashions. The Willsboro Heritage Society has developed the old bank building to serve as a museum to preserve the town's history.