DeWitt Clinton, for whom the county was named in 1835, lived from 1769 to 1828 and served nine years in the New York Senate and in the U.S. Senate in 1802-03, where he introduced the Twelfth Amendment establishing the present method of electing the U.S. president and vice president. He was mayor of New York for nine years and a leader in the tax-supported school movement, served as lieutenant governor from 1811 to 1813 and governor from 1817 to 1821 and 1825 to 1828, and sponsored the Erie Canal from 1816 to 1825. The county was formed from Cumberland and Wayne.