 US 45 debuted in Michigan by 1935 on maps of the time . The highway previously terminated in Des Plaines , Illinois , until it was extended northward to Michigan . US 45 replaced M @-@ 26 between the state line north toward Rockland , as well as M @-@ 35 between Rockland and Ontonagon . The Michigan State Highway Department ( MSHD ) rebuilt an eight @-@ mile ( 13 km ) section of the highway in the Military Hills area of eastern Ontonagon County starting in 1957 . As part of the project , tons of waste copper rock were hauled into the area to provide a base for the reconstructed roadway , which was previously quite steep through the hills and muddy during rains . The project included a new bridge over the Ontonagon River that opened in late 1959 . Along with this bridge , the last eight miles ( 13 km ) of US 45 in the country were paved , connecting the Gulf of Mexico and Lake Superior with a hard @-@ surfaced road . 
