Schenectady County is a county located in the U.S. state of New York. As of the 2010 census, the population was 154,727. It is part of the Albany-Schenectady-Troy Metropolitan Statistical Area. The county seat is Schenectady. The name is from a Mohawk Indian word meaning "on the other side of the pine lands" and is pronounced .
Schenectady County was formed in 1809. When counties were established in New York in 1683, the present Schenectady County was included in Albany County. Albany County 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.
From 1772 to 1786 Albany County included, besides the present territory of Albany County, all of the present Columbia, Rensselaer, Saratoga, and Schenectady Counties, parts of the present Greene and Washington Counties, and a piece of what is now southwestern Vermont.
Albany County was reduced in size in 1786 by the splitting off of Columbia County; again in 1791 by the splitting off of Rensselaer and Saratoga Counties and the transfer of the Town of Cambridge to Washington County. It was further reduced in size in 1795 by the splitting off of a part that was combined with a portion of Otsego County to create Schoharie County. It was further reduced in size in 1800 by the splitting off of a part that was combined with a portion of Ulster County to create Greene County.
In 1809, Schenectady County was split from Albany County.