It flows roughly due south, through extreme eastern South Dakota and passes through the city of Sioux Falls. South of Sioux Falls, it forms part of the boundary between South Dakota and Iowa, before flowing into the Missouri north of the city of Sioux City, Iowa.
Sioux City is at the navigational head of the Missouri River, about 90 miles north of the Omaha-Council Bluffs metropolitan area.
Sioux City and the surrounding areas of northwestern Iowa, northeastern Nebraska and southeastern South Dakota are sometimes referred to as Siouxland, especially by the local media.
Sioux City was laid out in 1854 by Dr. John K. Cook, sent by the United States Federal Government to survey northwestern Iowa, who was impressed by the location at the mouths of the BigSioux and Floyd Rivers at the Missouri.