Murdo is a city in and the county seat of Jones County, South Dakota, United States. The population was 475 at the 2020 census. Murdo was founded in about 1907 by the Chicago, Milwaukee, St. Paul and Pacific Railroad. As about halfway between Rapid City and Mitchell, Murdo was home to a roundhouse and a railyard, and a passenger station which served trains bound for Rapid City and Mitchell, until the discontinuation of the Sioux passenger train. The town was named in honor of cattle baron Murdo MacKenzie. United States Senator John Thune is from Murdo, South Dakota.