Major Rivers, Lakes, and Reservoirs in and Around South Dakota

Rivers

• Missouri River – Eastern border, longest in North America.
• Big Sioux River – Southeast border, tributary of Missouri.
• James River – Flows through eastern SD, joins Missouri near Yankton.

Major Reservoirs (on Missouri River)

• Lake Oahe – Largest U.S. reservoir by surface area (376,000 acres).
• Lake Sharpe – 57,000 acres, south-central.
• Lewis & Clark Lake – 26,000 acres, southeast.

Notable Landforms (Not Water)

Black Hills – Mountain range, Harney Peak (7,242 ft).
Badlands National Park – Erupted sedimentary formations.