What States Border South Dakota

North Dakota and South Dakota share a border along South Dakota's entire northern edge. The boundary follows a straight east-west line along a surveyed parallel.

The South Dakota-North Dakota border extends for about 360 miles from Montana in the west to Minnesota in the east. The border follows the 46th parallel north latitude, creating a perfectly straight line across the northern prairie. South Dakota counties along this border include Harding, Perkins, Corson, Campbell, McPherson, Brown, Marshall, Roberts, and Grant. The border crosses rolling plains and prairie country. Cities near this border include Aberdeen, South Dakota.

Minnesota borders South Dakota on the eastern side. The Big Sioux River forms the southern portion of this boundary, while surveyed lines create the northern section.

The South Dakota-Minnesota border runs for about 240 miles from North Dakota in the north to Iowa in the south. The northern portion follows a surveyed line, while the Big Sioux River creates a natural boundary in the south for about 100 miles. South Dakota counties along this border include Roberts, Grant, Codington, Deuel, Brookings, Moody, and Minnehaha. Sioux Falls, South Dakota's largest city, sits very close to this border in the southeast.

Iowa and South Dakota are separated by the Big Sioux River along South Dakota's southeastern corner. This short border is entirely formed by the winding river.

The South Dakota-Iowa border follows the Big Sioux River for about 50 miles from Minnesota in the north to Nebraska and the Missouri River in the south. The entire border is a water boundary. Only three South Dakota counties touch this border: Union, Lincoln, and Minnehaha. On the Iowa side, Lyon, Sioux, Plymouth, and Woodbury counties sit along the Big Sioux River. Sioux City, Iowa sits at the junction where South Dakota, Iowa, and Nebraska meet at the confluence of the Big Sioux and Missouri Rivers.

Nebraska forms South Dakota's entire southern border. The Missouri River creates the eastern portion of this boundary, while a straight surveyed line continues to the west.

The South Dakota-Nebraska border extends for about 425 miles from Iowa in the east to Wyoming in the west. The Missouri River forms roughly 350 miles of border in the eastern section, making this one of the longest river boundaries in the region. The western section follows a surveyed line. South Dakota counties along this border include Union, Clay, Yankton, Bon Homme, Charles Mix, Gregory, Tripp, Todd, Bennett, and Shannon. The border divides the Great Plains, with similar terrain on both sides.

Wyoming borders South Dakota on the western side. The boundary follows a straight north-south line along a surveyed meridian through the Black Hills region.

The South Dakota-Wyoming border runs for about 355 miles from Montana in the north to Nebraska in the south. The border follows a surveyed meridian line. South Dakota counties along this border include Harding, Butte, Lawrence, Meade, Pennington, Custer, and Fall River. The Black Hills, including Mount Rushmore and Custer State Park, sit near this border on the South Dakota side. Rapid City, South Dakota is the major city near this western border.

Montana borders South Dakota in the northwestern corner. This creates a point where Montana, South Dakota, Wyoming, and North Dakota nearly meet (though Montana and Wyoming don't actually touch at this point).

The South Dakota-Montana border extends for about 110 miles from North Dakota in the north to Wyoming in the south. The border follows a straight north-south meridian line through remote prairie and badlands country. Only two South Dakota counties touch this border: Harding and Butte. This is one of the most sparsely populated border regions in South Dakota. The northwestern corner of South Dakota includes portions of the Montana badlands landscape.