Ontario County Information Ontario County, NY was created in 1769 from Montogmery County. In 1795 the southeast corner of Ontario was split off to form Steuben County. In 1802 the western 3/4s of Ontario was detached to form Genesee County. In 1821 the western 1/4 of Ontario was split off to form parts of Livingston and Monroe counties. In 1823 the upper 1/3 and the lower 1/3 of Ontario were split off to form portions of Wayne and Yates counties
Note: Bloomfield was partitioned after the 1830 census and Geneva was split off from Seneca after 1830, |