**In South Dakota the maximum speed limit of 80 mph (129 km/h) is posted on rural freeways with 75 mph (121 km/h) in city maintained areas. The speed limit of 70 mph (113 km/h) is posted on a few four-lane highways and the speed limit of 65 mph (105 km/h) is found on other roads. The South Dakota and Minnesota state line has a speed limit of 70 mph (113 km/h) to match Minnesota’s maximum speed limit.**

The Interstate 90 stretch from Rapid City to the Wyoming Border is posted at 75 mph (121 km/h) due to safety concerns.