 State Route 100 ( SR 100 ) is a 4 @.@ 68 @-@ mile @-@ long ( 7 @.@ 53 km ) state highway in the U.S. state of Washington , serving Cape Disappointment State Park in Pacific County . The highway travels counterclockwise from U.S. Route 101 ( US 101 ) in Ilwaco south to Cape Disappointment and north to an intersection with itself in Ilwaco . SR 100 , part of the Lewis and Clark Trail Scenic Byway , serves as a loop route and has a spur route that serves the state park and a Coast Guard station . SR 100 was established in 1991 on the existing North Head Road , which was a paved county road by the late 1950s . The highway was washed away during a 1994 winter storm and had its spur route shortened in 2006 . 
