U.S. Route 18 (US 18) is an east–west U.S. highway in the Midwestern United States. The western terminus is in Orin, Wyoming at an interchange with Interstate 25. Its eastern terminus is in downtown Milwaukee, Wisconsin. However, US 18 runs concurrent with other U.S. routes from its western terminus to Mule Creek Junction, Wyoming. US 18 is one of the original United States highways of 1926. The US 18 designation was originally proposed for a road in Michigan from Grand Haven east to Detroit. This roadway was eventually designated as U.S. Route 16. Route description Wyoming In Wyoming, US 18 runs concurrent with U.S. Route 20 from Interstate 25 to Lusk, where US 18 branches off to run concurrently with U.S. Route 85. At the unincorporated community of Mule Creek Junction in northeastern Niobrara County, US 18 leaves US 85. This ten-mile (16 km) stretch from US 85 to the South Dakota border is the only segment of US 18 in Wyoming which is not co-signed with another highway. Running for nearly 100 miles, US 18 has a speed limit of 70 MPH with the exception of its ending terminus at Orin and the portion throughout Lusk. South Dakota U.S. 18 enters South Dakota west of Edgemont. It passes through Hot Springs, the Pine Ridge Indian Reservation, the Rosebud Indian Reservation, Winner, and Gregory before crossing the Missouri River near Pickstown over the Fort Randall Dam. East of the Missouri River, U.S. 18 passes through (or near) Lake Andes and Tripp before a brief concurrency with Interstate 29 near Worthing. East of I-29, U.S. 18 passes through Canton before crossing the Big Sioux River into Iowa. The Oyate Trail is one of the names given (in the late 1990s) to the section of US-18 traveling across South Dakota from I-29 east of Vermillion to Maverick Junction. Named in an attempt to encourage more tourism traffic through the lands of various AmerInd tribes in southern South Dakota, it passes through or near the Yankton Sioux Indian Reservation, the Rosebud Indian Reservation, and the Pine Ridge Indian Reservation, crossing the James River Valley, the Missouri River near Fort Randall Dam, portions of Pine Ridge, and the High Plains of South Dakota, connecting the urban areas of the middle Missouri River with the Black Hills. Portions of the road were known as the Grant Highway, Black Hills Sioux Trail, and as part of