When the
Joint Board on Interstate Highways submitted its report in October 1925 proposing the United States Numbered Highway System, Route No. 10 was planned to travel eastward from Seattle to Minneapolis–St. Paul, then southeast to Chicago, then northeast to Detroit. In the same proposal,
U.S. Route 12 was intended to cross US 10 near Minneapolis, travel eastward through Wisconsin, make use of the Lake Michigan ferry connecting Manitowoc, Wisconsin, to Ludington, Michigan, and then travel eastward to the same endpoint in Detroit. In the finalized system, approved on November 11, 1926, these designations east of the Twin Cities were switched, with US 10 using the ferry and US 12 rounding the southern end of Lake Michigan at Chicago. In 1986, the segment of US 10 between Wye and West Fargo, North Dakota, was decommissioned, reducing the route to its current western terminus. Some sections of the old US 10 road still exist in such cities as
Bismarck,
Missoula,
Spokane, and between
Cle Elum and
Ellensburg as Washington State Route 10 (SR 10). The last section of I-90 to be completed was between
Coeur d'Alene and
Wallace in the early 1990s. Much of this route was conumbered as both I-90 and US 10 until the final completion of I-90 through Idaho. Some decommissioned sections of US 10 are designated
I-90 Business (I-90 Bus.) or
I-94 Bus. routes. At least four US 10 Alternate (US 10 Alt.) routes were used, including
one from Spokane to Missoula from 1941 to 1967 via
Sandpoint, Idaho (represented today by
US 2,
State Highway 200,
MT 200, and
US 93), US 10 Alt. between US 10 (4th Avenue S. and Dearborn Street in Seattle) and present-day US 2 in Everett (Rucker Avenue and Hewitt Avenue) along
US 99, US 10 Alt. between the western terminus of US 10 and Issaquah along the pre-truncated version of
SR 900, and the Pintler Scenic Route through
Philipsburg, and
Anaconda, renamed
MT 1 when Montana's US 10 was decommissioned in 1986. US 10 split between
Garrison and
Three Forks into US 10N and US 10S from 1936 until 1960. US 10N through
Helena and dropping into Three Forks, while the Southern section of the split followed US 10's traditional routing through
Deer Lodge and
Butte, Montana, to get across the Rocky Mountains. Previous to the split, US 10N was designated as another US 10 Alt. At the eastern end, US 10 originally went south from
Midland to
Saginaw, Michigan, on what is now highway
M-47. It then joined up with
US 23 in Saginaw and continued south until it split from US 23 near
Flint. It then continued southeast as the
Dixie Highway to
Pontiac, where it followed Woodward Avenue, now designated
M-1. From there, US 10 continued on an almost straight line to
Downtown Detroit, where it intersected
US 16,
US 25, and
US 12. at which point the Lodge Freeway was redesignated to
M-10. In 2015, the
American Association of State Highway and Transportation Officials officially designated the car ferry as part of the highway's official route, joining
US 9 as the only two routes with a ferry connection. ==Major intersections==