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. The wagon road was maintained by the county government as County Road 1 until it was transferred to state control in 1937 and became part of Secondary State Highway 9A (SSH 9A), a highway connecting
Sappho to
Port Angeles via
Pysht. The state government purchased
right of way in 1947 to extend SSH 9A to Neah Bay, a year before the existing highway was paved. By 1953, a road extending from
Neah Bay to SSH 9A was completed and in June 1955, the roadway was added to SSH 9A, while the Sappho segment was deleted. A southern extension of SSH 9A to connect with US 101 near Queets, part of an extended coastal route to
Hoquiam, was first proposed in the 1940s. The proposed highway was supported by the Clallam County government, who lobbied for a full study from the state government. The proposal was opposed by conservationists, who embarked on a coastline hike in August 1958 and was joined by U.S. Supreme Court Justice
William O. Douglas. The coastal highway was shelved for several years but approved by the
U.S. Bureau of Outdoor Recreation in 1964, prompting more protests that resulted in its cancellation. During the
1964 highway renumbering, SSH 9A became SR 112; the highway became a state scenic byway in 1967. The Sappho segment of SSH 9A later was readded to the state highway system in 1991 as . On June 15, 2000, SR 112 became a
National Scenic Byway named the Strait of Juan de Fuca Highway. The designation came amid efforts to restore the natural habitat of the region after decades of logging and erosion. It was dedicated in 2001 by local officials and representatives from the tourist and timber industries. The western section of SR 112 and SR 113 were designated as the "Korean War Veterans Blue Star Memorial Highways" by the state legislature in 2007 and dedicated in 2014. Various sections of SR 112 have been damaged or destroyed by
landslides, particularly those caused by winter storms, since the 1960s. A major landslide in early 1990 prompted WSDOT to consider abandonment of the highway between Burnt Mountain Road (now SR 113) and Port Angeles. A
late December winter storm in 2008 resulted in floods that triggered a landslide that closed the highway near
Joyce on January 8, 2009. Temporary repairs began on March 2 and only one-way traffic was allowed until the roadway reopened on March 12. Another set of five landslides in January 2021 caused several sections to be closed, including near the Pysht River. The highway was fully reopened in July. ==Major intersections==