Chenango County is a county located in the U.S. state of New York. As of the 2010 census, the population was 50,477. The county's name originates from an Oneida word meaning "large bull-thistle." Its county seat is Norwich.
When counties were established in what is now the American state of New York in 1683, the present Chenango 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 even though territories located to the west of present-day Pennsylvania were under effective French control as part of New France. 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 Montgomery County in honor of 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.
Chenango County was formed on March 15, 1798 from of Tioga and Herkimer Counties.
On March 21, 1806, of Chenango County was partitioned to produce Madison County. This produced Chenango County as it exists today.