It travels 48 miles (77 km) along the Pacific Coast between two junctions with U.S. Route 101 (US 101) in Raymond to the south and Aberdeen in the north.

The highway also has two spur routes: a 4-mile (6 km) road serving the city of Westport on Grays Harbor and a short connector in Aberdeen.

The highway then passes through Ocosta and near the Stafford Creek Corrections Center before entering the city limits of Aberdeen.

SR 105 turns north onto Boone Street near the Grays Harbor College campus and the Shoppes at Riverside shopping mall.

The SR 105/105 Spur junction is about 5 miles (8 km) north of Grayland, Washington, immediately adjacent to Twin Harbors State Park.

[1] WSDOT estimates that daily traffic on the spur route ranges from 1,000 vehicles at its northern terminus to 5,400 at Montesano Street.

[14] Between Grayland and Tokeland, SR 105 had to be re-routed inland in the 1990s from Cape Shoalwater, due to currents coming out of Willapa Bay causing severe erosion, taking many acres of land out to sea.