In South Dakota, the landscape of water is one of dramatic change and massive engineering. To find the largest lake in the state, you have to look toward the Missouri River for an artificial giant that defines the central plains, or toward the glacial "prairie potholes" of the east for a natural lake that has undergone a remarkable transformation in recent decades.
The Man-Made Giant: Lake Oahe
Lake Oahe is the undisputed heavyweight of South Dakota's waters. Created by the Oahe Dam on the Missouri River in the 1960s, it is the fourth-largest reservoir in the United States by volume and stretches for over 200 miles across the heart of the state.
- Surface Area: Approximately 370,000 acres.
- Shoreline: 2,250 miles—more than the entire length of the California coast.
- Maximum Depth: 205 feet near the dam.
- Location: Central South Dakota, stretching from Pierre into North Dakota.
Named after the 1874 Oahe Indian Mission, this massive lake is a hub for high-energy recreation. It is world-renowned for its walleye fishing, but it also supports healthy populations of Northern Pike and Chinook Salmon. Because of its sheer length, the lake traverses several different landscapes, from the bustling state capital of Pierre to the remote, rugged breaks of the Standing Rock and Cheyenne River Sioux Reservations.
The Natural Wonder: Lake Thompson
While South Dakota has many natural glacial lakes, Lake Thompson holds the title of the State largest natural body of water. However, its status is a relatively recent development in geological terms.
- Surface Area: Fluctuates based on rainfall, historically reaching up to 20,000 acres.
- Location: Kingsbury County, near De Smet in east-central South Dakota.
For much of the early 20th century, Lake Thompson was little more than a marshy wetland; in fact, it was completely dry during the Dust Bowl of the 1930s. Dramatic flooding in the 1980s and 90s transformed the basin into a permanent, expansive lake that submerged thousands of acres of former farmland and trees. Today, it is a National Natural Landmark and a premier destination for waterfowl hunting and fishing. Fans of pioneer history may recognize the area from the "Little House" books by Laura Ingalls Wilder, who lived in nearby De Smet and wrote about the "Twin Lakes" of the region.
South Dakota's water features offer a study in scale and resilience. Lake Oahe stands as the State massive artificial backbone, a 231-mile-long reservoir that provides endless shoreline for anglers and boaters. In contrast, Lake Thompson represents the State natural heritage, having evolved from a dry marsh into South Dakota's largest natural lake, offering a unique high-water landscape that serves as both a historic landmark and a thriving wildlife sanctuary.