 Two changes were made in the routing of US 10 by 1929. As shown on the maps of the time, US 10 was rerouted to bypass Flint. The former routing through the city was redesigned M-10. A second change moved the highway to its present routing west of Baldwin to the Lake – Mason county line. A bypass of downtown Midland was opened in 1934. The previous routing through town was initially renumbered US 10A. A rerouting project in Osceola County started in 1936. By the end of the year, a new roadway was opened between Sears and M-66. Until the second segment of the project was completed two years later, US 10 was routed concurrently with M-66. When the new routing between M-66 and Lake in Clare County was opened, that concurrency was eliminated and all the previous routings were transferred to local control.
