Yates County is a county located in the U.S. state of New York. As of the 2010 census, the population was 25,348, making it the third-least populous county in New York. The county seat is Penn Yan. The name is in honor of Joseph C. Yates, who as Governor of New York signed the act establishing the county.
When counties were established in New York State in 1683, the present Yates 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, Tryon County, contained the western portion (and thus, since no western boundary was specified, theoretically still extended west to the Pacific). The eastern boundary of Tryon County was approximately five miles west of the present city of Schenectady, and the county included the western part of the Adirondack Mountains and the area west of the West Branch of the Delaware River. The area then designated as Tryon County now includes 37 counties of New York State. The county was named for William Tryon, colonial governor of New York.
In the years prior to 1776, most of the Loyalists in Tryon County fled to Canada. In 1784, following the peace treaty that ended the American Revolutionary War, the name of Tryon County was changed to honor the general, Richard Montgomery, who had captured several places in Canada and died attempting to capture the city of Quebec, replacing the name of the hated British governor.
On January 27, 1789, of Montgomery County was split off to create Ontario County, including the lands of the present Allegany, Cattaraugus, Chautauqua, Erie, Genesee, Livingston, Monroe, Niagara, Orleans, Steuben, Wyoming, and Yates counties, and part of Schuyler and Wayne counties.
On March 18, 1796, of Ontario County was partitioned to form Steuben County.
On April 3, 1801, Ontario County exchanged land with Cayuga County, and lost as a result.
On March 30, 1802, Ontario County lost of land through the partition of Genesee County, including the present Allegany, Cattaraugus, Chautauqua, Erie, Niagara, Orleans and Wyoming counties and parts of Livingston and Monroe counties.
In 1821, Ontario County was reduced in size by combining portions of Genesee and Ontario counties to create Livingston and Monroe counties.
On April 15, 1828, was partitioned from Yates, and passed to Seneca and Tompkins counties, mostly in the forest.
On March 17, 1860, Ontario County was authorized to gain land from Yates, but it was never put into effect.
On April 18, 1946, Yates gained from Schuyler and Senaca counties, which produced the current borders of Yates County.