The highway, part of the Lewis and Clark Trail Scenic Byway,[3][4] travels west on Spruce Street through an intersection with the clockwise terminus of SR 100, on 2nd Avenue, and continues towards the Pacific Ocean on North Head Road.

SR 100 turns south along the Pacific coast past North Head Lighthouse and into Cape Disappointment State Park on Robert Gray Drive.

The highway intersects its spur route that travels south on Fort Canby Road towards Coast Guard Station Cape Disappointment.

[7] The North Head Road portion of SR 100, traveling west from Ilwaco to the Pacific coast and south to Cape Disappointment within Fort Canby State Park, has existed as a paved roadway since 1957.

[10] Robert Gray Way was rebuilt after a 1994 winter storm washed away the roadway into Baker Bay.