High Quality Content by WIKIPEDIA articles! US Highway 45 (US 45) is a part of the United States Numbered Highway System that runs from Mobile, Alabama, to the Upper Peninsula (UP) of the US state of Michigan. The highway forms a part of the state trunkline highway system that is maintained by the Michigan Department of Transportation (MDOT). It enters the state from Wisconsin south of Watersmeet, ending at Ontonagon. In between, the roadway crosses the UP running through the Ottawa National Forest and running along the Ontonagon River.