Sioux Falls is the largest city in the U.S. state of South Dakota. Sioux Falls is the county seat of Minnehaha County, and also extends into Lincoln County to the south. It is the 47th fastest growing city in the United States and the fastest growing metro area in the State of South Dakota, with a total increase of 22% since 2000. Sioux Falls revolves around the cascades of the Big Sioux River. The falls were created about 14,000 years ago during the last ice age.