What is known today as the North Cascades Highway was originally the corridor used by local Native American tribes as a trading route from
Washington's Eastern Plateau country to the Pacific Coast for more than 8,000 years. After the
California Gold Rush of 1849, white settlers started to arrive in the North Cascades looking for gold as well as fur-bearing animals. This far north, the settlers needed a clear route through some of the most rugged terrain in
Washington Territory. is due east of Washington Pass. It wasn't until 1895, however, that funding to explore a possible route through the Cascade Range was appropriated. After one year of surveying possible routes in the Upper Skagit River region, the State Road Commission concluded in 1896 that the
Skagit gorge was not a practical route. Instead, the commission settled upon the
Cascade Pass route, several miles south of the Skagit gorge. The Cascade Pass route began to be roughed out in 1897 and shortly afterward, state highway maps showed the road as either State Highway 1 or the Cascade Wagon Road. In the following years, floods on the
Cascade River took out most of the work completed on the road and led
Washington's first State Highway Commissioner to report in 1905 that almost all the money appropriated for the road had been wasted. After these unsuccessful attempts to build a northern cross-mountain highway, the state designated that a highway be built along the
Methow River from
Pateros to
Hart's Pass, high above Eastern Washington's
Methow Valley. This road was completed in 1909. By 1936, both of
Seattle City Light projects,
Gorge Dam and
Diablo Dam, had been completed and were attracting visitors and families to the area. In 1940, the first stage of the completion of
Ross Dam was reached. Because this influx of population and interest in the area once again demonstrated the need for a northern route over the high
Cascades, highway promoters began to try to persuade other boosters to finally abandon the idea of the ill-fated Cascade Pass route and instead look to agreeing on a route across
Rainy and
Washington Pass. In 1953, the North Cascades Highway Association was formed with politicians, lobbyists, and business owners from both sides of the North Cascades taking part. As these boosters pushed
Olympia harder to move forward on the highway plan, more and more requests for huge sales of old-growth timber from along the highway corridor came in. These increasing timber requests were used to support the need for a highway. Finally, in 1958, the State of Washington appropriated funds to build a highway from the Seattle City Light company town of Diablo to Thunder Arm, a southern arm of
Diablo Lake. Funds were also allotted to improve access roads on both sides of the North Cascades and construction on this section of the highway began in 1959. The corridor was designated as Primary State Highway 16 (PSH 16) in 1962, replacing several earlier designations that were shared with other highways. Over the next nine years, construction of the road continued along with the signing of the
North Cascades National Park bill by President
Lyndon B. Johnson in 1968. With this bill, the hope of using the highway as access for high-dollar timber sales was quashed. Nonetheless, businessmen and residents on both sides of the North Cascades were hopeful and supportive of the tourist dollars that would be seen with the opening of the "North-Cross Highway". The North Cascades Highway officially opened on September 2, 1972, with a procession led over Washington Pass by governor
Dan Evans and President
Richard M. Nixon's brother
Edward. The highway's construction came with conservation measures and upgrades to camping facilities in the then-new
North Cascades National Park to handle the expected traffic. During the first weekend, an estimated 8,000 people visited the Washington Pass overlook. The
Methow Valley town of
Winthrop renovated its buildings into an
Old West theme with false-front buildings and boardwalk sidewalks in a bid to attract tourists on the new highway. For several weeks in August 2023, the Newhalem–Rainy Pass section of SR 20 was closed due to the
Sourdough Fire and Blue Lake Fire.
Associated routes From 1964 until 1973, SR 20 was designated as SR 113 from
Discovery Bay to
Coupeville. The route had historically been the
Port Townsend branch of (PSH 9 PT) and a branch of (SSH 1D) in 1937, during the creation of the
Primary and secondary highways. In 1964, these two highways became SR 113, as part of a new numbering system created by the
Washington State Legislature and the
Washington State Department of Transportation. The Port Townsend–
Keystone ferry wasn't technically part of SR 20 until 1994 when all of the
Washington State Ferries routes were added to the state highway system. From Coupeville to Sharpes Corner (just outside
Anacortes), the modern SR 20 was designated
SR 525, and prior to 1964 as SSH 1D. When the North Cascades Highway was completed, and the SR 20 designation extended Westward, the SR 525 designation was supplanted to Coupeville. From Mt. Vernon to the Anacortes Ferry Terminal, the modern SR 20 (and SR 20 Spur, west of Sharpes Corner) was designated
SR 536, and prior to 1964 as the Anacortes Branch of PSH 1. When the North Cascades Highway was completed, and the SR 20 designation extended westward, the SR 536 designation was supplanted, and the SR 20 Spur designation created to keep the route to the ferry terminal within the highway system. From 1964 to 1973, the route from
Colville to
Tiger was designated as SR 294, and the route from Tiger to
Newport as SR 31. ==Major intersections==