In between, the roadway crosses the UP running for approximately 54+3⁄4 miles (88.1 km) through the Ottawa National Forest and parallel to the Ontonagon River.

An eight-mile (13 km) segment was significantly reconstructed in the late 1950s, and an alignment change in the 1970s moved the routing of US 45 near Rockland before it was reversed soon afterwards.

A segment of roadway that formerly carried US 45 is the site of the Paulding Light, a local phenomenon whose origins were scientifically described in 2010.

East of Rockland, US 45 meets the southern terminus of M-26; after the intersection, US 45 turns northwesterly and runs parallel to the Ontonagon River[4][5] and a snowmobile trail (a former branch of the Escanaba and Lake Superior Railroad).

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.

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.

[15][16] In 2010, students from Michigan Technological University solved the mystery of the Paulding Light, a local phenomenon commonly attributed to paranormal activity.