American Highway Code US Route 21 History
. US-16 originally connected Detroit, Michigan with Yellowstone, including a ferry link across Lake Michigan between Muskegon, Michigan and Milwaukee, Wisconsin.
. In Michigan, the route was in use long before automobiles and was known to white settlers as the Grand River Trail, and prior to the designation of U.S. routes in 1926, had been designated as M-16 in the 1920s from Detroit to south of Muskegon.
. In 1938, reflectorized discs were placed on US-16 every 100 feet (30 m) from Detroit to Lansing, resulting in fewer nighttime traffic accidents. Other states would later do the same on their roads.
. US 16 initially crossed the South Dakota-Wyoming state line west of Spearfish. U.S. Route 216 was commissioned in 1930 as a loop off US 16 to the south between Rapid City and Moorcroft, crossing the state line west of Custer.In 1934, US 16 was moved to the US 216 alignment, while the former US 16 became part of an extension of US 14.
. In Michigan, most of US-16 was superseded by Interstate 96 and a segment of Grand River Avenue in Detroit ultimately became M-5. US-16 was later decommissioned in Wisconsin,Minnesota, and eastern South Dakota to its present termini. Between Rapid City and Dexter, Minnesota, it has been supplanted by Interstate 90.
. East of there it is now Minnesota State Highway 16 and Wisconsin Highway 16. In South Dakota it was replaced by various state highways (including SD Highway 38) and county roads: generally, in West River the old alignment was transferred to county responsibility entirely, while in East River it remained a state-maintained highway.
. What remains of US 16 is a route that passes through the towns of Cody, Wyoming, Greybull, Wyoming, Worland, Wyoming, Buffalo, Wyoming, Gillette, Wyoming,Newcastle, Wyoming, and Custer, South Dakota and gives good access to Mount Rushmore. Between Buffalo and Rapid City, Interstate 90 is a much more direct (but not necessarily more scenic) route.
. An "Alternate US 16" passes through Powell, Wyoming[citation needed]; an older Alternate US 16 in South Dakota has become South Dakota State Highway 240.
