Minnehaha County is a county on the eastern border of the state of South Dakota. As of the 2020 census, the population was 197,214, making it the state's most populous county. It contains over 20% of the state's population. Its county seat is Sioux Falls, South Dakota's most populous city. The county was created in 1862 and organized in 1868. Its name was derived from the Sioux word Mnihaha, meaning "rapid water," or "waterfall".