The Town of Essex is on the eastern edge of the county. It is south-southwest of Burlington, VT which is on the other shore of Lake Champlain, south of Plattsburgh, south of Montreal, Quebec, and north of Albany, NY. Essex is inside the Adirondack Park.
Essex was part of a land grant made to Louis Joseph Robart by French King Louis XV. The land grant was lost after the British took over the region after 1763.
The region was first settled around 1765 with the intention of forming a baronial estate like those of the lower Hudson River for landowner and investor, William Gilliland.
The town was formed from a part of the Town of Willsboro in 1805. It was an important shipbuilding location and port, but that economy collapsed after 1849 with the beginning of railroad lines in the region.