Auto dealer license in South Dakota is about to be introduced. Minnehaha County is a county located in the U.S. state of South Dakota. From the 2010 census, the population was 169 468, which makes the most populous county in South Dakota. Its county seat is Sioux Falls. County takes its name from the Sioux Indian word “Mnihaha”, which is often mistakenly translated as “laughing water”, but actually meaning “water fast” or “cascade”. The original word changed the spelling of the current, when the pronunciation easier. Minnehaha County is a part of Sioux Falls, SD, Metropolitan Statistical Area.