Todd County is a county located in the U.S. state of South Dakota. As of the 2010 census, the population was 9,612. Todd County does not have its own county seat. Instead, Winner in neighboring Tripp County serves as its administrative center. Its largest city is Mission. The county was created in 1909, although it remains unorganized. The county was named by European-American settlers after John Blair Smith Todd, who was a delegate from Dakota Territory to the United States House of Representatives and a general in the Union Army during the American Civil War.