Grant County is a county located in the northern part of the U.S. commonwealth of Kentucky. As of the 2020 census, the population was 24,941. Its county seat is Williamstown. The county was formed in 1820 and named for Colonel John Grant, who led a party of settlers in 1779 to establish Grant's Station, in today's Bourbon County, Kentucky. Grant County is included in the Cincinnati-Middletown, OH-KY-IN Metropolitan Statistical Area.