Clay County is a county located in the U.S. state of Texas. As of the 2020 census, its population was 10,218. The county seat is Henrietta. The county was founded in 1857 and later organized in 1860. It is named in honor of Henry Clay, famous American statesman, Kentucky Senator and United States Secretary of State. Clay County is part of the Wichita Falls, Metropolitan Statistical Area in North Texas.