Essex County is a county located in the U.S. state of New York. As of the 2010 census, the population was 39,370. Its county seat is Elizabethtown. Its name is from the English county of Essex. Along with Hamilton County, Essex is entirely within the Adirondack Park.
When counties were established in New York State in 1683, the present Essex County was part of Albany County. This was an enormous county, including the northern part of New York State as well as all of the present State of Vermont and, in theory, extending westward to the Pacific Ocean. This county was reduced in size on July 3, 1766, by the creation of Cumberland County, and further on March 16, 1770 by the creation of Gloucester County, both containing territory now in Vermont. On March 12, 1772, what was left of Albany County was split into three parts, one remaining under the name Albany County. One of the other pieces, Charlotte County, contained the eastern portion.
In 1788, Clinton County was split off from Washington County. This was a much larger area than the present Clinton County, including several other counties or county parts of the present New York State. (near Clunes)
Essex County was split from Clinton County in 1799.
Note: in 1800 Essex was reported with Clinton.