State highway in St. Clair County, Michigan, United States
M-136 is a state trunkline highway in the US state of Michigan that runs from Brockway to Fort Gratiot in the lower part of The Thumb of the Lower Peninsula. The highway serves as a connector between M-19 on the west and M-25 northwest of Port Huron. In between, the highway runs through rural St. Clair County through farm fields and along a creek and river. The trunkline uses roads that were part of the state highway system in 1919. The M-136 designation was assigned in 1931 and extended to its current length in 1961.