The 295 mile long Big Sioux River (SOO), rises near the Grant/Day County lines southeast of
Waubay, and flows mostly south past
Watertown and
Pelican Lake, then past
Castlewood and
Bruce, near
Brookings and
Sioux Falls. There it receives Pipestone Creek from Minnesota, then forms the Iowa-South Dakota state line, continuing south past
Canton, and Akron (Iowa), to join the
Missouri River at Sioux City (Iowa).
The river nutures an agricultural region that produces corn, soybeans, oats, hogs, and beef cattle.
