Interstate 190 (I-190) is an auxiliary Interstate Highway in the US state of South Dakota. The route runs for about two miles (3.2 km) connecting I-90 to downtown Rapid City. Its length from I-90 to Omaha Street runs concurrent with US Highway 16 (US 16). It is the westernmost auxiliary route of I-90 (approximately 1,190 miles [1,920 km] east of the highway's western terminus in Seattle, Washington) and its only auxiliary route west of the Mississippi River.