Jones County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 917, making it the least populous county in South Dakota. Its county seat is Murdo. Created in 1916 and organized in 1917, it is the most recently established county in South Dakota. It was named after Granville Whittington Jones, an Arkansas-born clergyman/lawyer, who moved to Chamberlain, SD and became a noted Chautauqua speaker.