What’s the Largest Man-Made Lake in South Dakota?

Written by Kristin Hitchcock
Updated: September 25, 2023
© iStock.com/Chaden Roggow
Share this post on:


Lake Oahe is the largest man-made lake in South Dakota and the fourth-largest reservoir in the United States. The construction of the Oahe dam on the Missouri River in 1958 formed the Lake Oahe reservoir.

The dam is about 1,123 miles upstream from the mouth of the river in central South Dakota and about six miles northwest of the state capital Pierre. The lake extends up the river about 231 miles, nearly to Bismarck, ND, and has an area of 370,000 acres, a shoreline of 2,250 miles, and a maximum depth of 205 feet.

Lake Oahe is the largest reservoir in South Dakota.

Lake Oahe History

Before the Dam

Built as part of the Pick-Sloan Missouri Basin, the US Army Corps of Engineers and the Bureau of Reclamation were responsible for the dam’s construction. This program was part of the Flood Control Act of 1944, which included the construction of six dams in the Missouri River valley to provide flood control, power generation, steady water supply, irrigation, and recreational opportunities.

Lewis A. Pick developed the “Pick” plan after the House Flood Control Committee chose the Corps to develop a plan to reduce the extreme flooding in the Missouri river basin.

Additionally, William G. Sloan developed the “Sloan” plan. Sloan was the assistant director at the Bureau of Reclamation’s regional office and had previously worked for the Corps. The Omaha conference in the fall of 1944 consolidated both plans. Of the 113 different projects proposed, 107 projects remained, including 107 dams, 1,500 miles of levees, 4.7 million acres of irrigation systems, and 1.6 million kilowatts of power generation.

President Franklin D. Roosevelt signed a bill in 1944 that authorized $200 million for the program.

Impact on Native Americans

The Pick-Sloan program was the single most destructive act to indigenous tribes in the United States. The upland region along the river contained hearty native grasses that, many years ago, supported a massive buffalo population. Many Indigenous tribes naturally lived near the river, with plenty of water, timber, and abundant hunting grounds nearby.

The construction of dams and reservoirs in Missouri flooded thousands of acres of Indigenous reservations. The Oahe dam flooded 200,000 acres of the Standing Rock Reservation and Cheyenne River Reservation alone. Huge populations of indigenous people were thus forced to leave their ancestral lands. Sitting Bull, a famous Sioux leader, is thought to be buried near Lake Oahe in two possible locations.

The dam and the reservoir are named after the Oahe Mission, organized by Rev. Thomas L Riggs in 1874. Oahe means “a place to stand on” among the Sioux. The mission was located about 5 miles north of the Dam on Preoria bottom and included a school, Riggs’s home, and a Chapel built in 1877. The mission served the nearby Indigenous peoples until 1914. The chapel was moved to higher ground in 1957, and the other structures were destroyed. The chapel was moved near the dam in 1964 and still stands today as a historical landmark.


Lake Oahe
The deepest lake in South Dakota is Lake Oahe. This man-made reservoir is the deepest and biggest lake in South Dakota.


Construction began on the Oahu dam in 1948 and continued for ten years until 1958. More than 93 million cubic yards of dirt, rock, and concrete were used to form the dam and surrounding structures. At the time, the dam was the second-largest rolled-earth dam in the world.

It is 245 feet high, 9,360 feet long, has eight 50-foot x 23.5-foot tainter gates, and seven hydroelectric turbines that can produce up to a total of 786 megawatts of electricity. The final closure of the dam began on August 2, 1958. Around 3200 cubic yards per hour of shale were dumped into the river using heavy equipment, completing the final closure in just 21 ½ hours. It took nearly four years for the reservoir to fill the “minimum operating pool,” which is the level required for hydroelectric generation.

On August 17, 1962, President John F. Kennedy visited the dam for dedication, marking the first day it started generating power.

Lake Oahe Today

Lake Oahe
The Oahe Lake varies in deepness, with shallower depths near the shoreline and some of the deepest spots near the Oahe Dam.

©Chadden Roggow/Shutterstock.com

Recreational activities on Lake Oahe are abundant since the lake is so large. The lake is clear, deep, and wide, perfect for boating and fishing.

Over 2 million visitors enjoy the lake annually, with easy access from over 50 recreation areas. These areas vary from primitive to modern, with campgrounds, boat ramps, and marinas. Wildlife is in abundance in the area. Humans have hunted the area for nearly 9,000 years, and hunting big game is still popular today. Birds that frequent the area range from Bald Eagles to the endangered Least Tern and threatened Piping Plover.

The lake is a major stopover area for migratory birds, providing waterfowl hunters with excellent late-season opportunities. For anglers, the lake has various habitats that support large populations. Walleye is the most popular fish. You’ll also find channel catfish, smallmouth bass, northern pike, and even salmon stocked in the lake. During the winter, ice fishermen enjoy the lake. Lake Oahe is a true outdoorsman’s paradise, with year-round hunting, fishing, and recreational opportunities.

Where Is Lake Oahe Located on a Map?

Lake Oahe stretches from Pierre, South Dakota to Bismarck, North Dakota. Pierre is eight miles away. Two bridges over the lake are U.S. Route 212 west of Gettysburg, South Dakota and U.S. Route 12 at Mobridge. The city of Mobridge is situated on the eastern shore of the middle section of the lake.

Share this post on:

Thank you for reading! Have some feedback for us? Contact the AZ Animals editorial team.

  1. Wikipedia, Available here: https://en.wikipedia.org/wiki/Lake_Oahe
  2. USACE, Available here: https://www.nwo.usace.army.mil/Missions/Dam-and-Lake-Projects/Missouri-River-Dams/Oahe/
  3. South Dakota Missouri River Tourism, Available here: https://www.sdmissouririver.com/explore-adventure/the-big-lakes-rivers/
  4. Internet Archive Way Back Machine, Available here: https://web.archive.org/web/20110614085755/http://www.nwo.usace.army.mil/html/Lake_Proj/brochures/Oahe_brochure.pdf
  5. Oahe Reservoir, Available here: https://www.nps.gov/parkhistory/online_books/lecl/oahe-reservoir/sec2.htm
  6. South Dakota Public Broadcasting, Available here: https://www.sdpb.org/blogs/images-of-the-past/building-oahe-dam-1948-1959/