Lexington is a city in Cleveland County, Oklahoma, United States. The city population was 2,010 at the 2020 census, a 6.6% decrease from 201…Lexington is a city in Cleveland County, Oklahoma, United States. The city population was 2,010 at the 2020 census, a 6.6% decrease from 2010. Lexington is located in southern Cleveland County. It is bordered on the west by the Canadian River, which forms the McClain County line. The city of Purcell is directly across the river from Lexington, connected by U.S. Route 77. US 77 leads north from Lexington 16 miles to Norman and 38 miles to the center of Oklahoma City.