Washington State Route 100

State Route 100
SR 100 is highlighted in red.
Route information
Auxiliary route of US 101
Defined by RCW 47.17.163
Maintained by WSDOT
Length:	4.68 mi (7.53 km)
Existed:	1991 – present
Tourist routes:	Lewis and Clark Trail Scenic Byway
Major junctions
CCW end:	US 101 in Ilwaco
CW end:	SR 100 in Ilwaco
Location
Counties:	Pacific
Highway system
State highways in Washington Interstate US State Scenic Former PSH 1964 renumbering Former ← SR 99T US 101 →

State Route 100 Spur
Location:	Cape Disappointment State Park
Length:	0.080 mi (0.13 km)
Existed:	1991–present

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.

SR 100 begins at an intersection with US 101 in Ilwaco as the highway turns north onto 1st Avenue towards Seaview. The highway, part of the Lewis and Clark Trail Scenic Byway, 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. SR 100 turns north and travels into Ilawaco along Baker Bay and the Columbia River before it ends at an intersection with SR 100 a block from its terminus at US 101.