It runs east–west for 61 miles (98 km) along the Strait of Juan de Fuca in Clallam County, connecting the Makah Indian Reservation near Neah Bay to U.S. Route 101 (US 101) near Port Angeles.

The highway continues west as Bayview Avenue to Neah Bay and Cape Flattery, the northwesternmost point in the contiguous United States.

[2] SR 112 travels southeast along the Strait of Juan de Fuca, following a meandering path along the forested foothills of the Northwest Olympic Mountains and crossing several creeks and streams.

[5] The highway leaves the Clallam River and reaches the foothills of Burnt Mountain at a junction with SR 113, which travels south to US 101 at Sappho.

[3][5] SR 112 is designated as the Strait of Juan de Fuca Highway, a National Scenic Byway that covers all 61 miles (98 km) of the route.

[3] The northwestern reach of the Olympic Peninsula was open to logging and settlement in the late 19th century, and a rough trail along the Strait of Juan de Fuca was used by American emigrants.

[20][21] The proposal was opposed by conservationists, who embarked on a 22-mile (35 km) coastline hike in August 1958 and was joined by U.S. Supreme Court Justice William O.

[35] A major landslide in early 1990 prompted WSDOT to consider abandonment of the highway between Burnt Mountain Road (now SR 113) and Port Angeles.