List of Primary State Highways in Washington

The first state road, running across the Cascade Range roughly where State Route 20 now crosses it, was designated by the legislature in 1893 (However, this road wasn't actually opened until 1972). Two other roads—a Cascade crossing at present State Route 410 and a branch of the first road to Wenatchee—were added in 1897. The Washington Highway Department was established in 1905, and a set of twelve State Roads, numbered from 1 to 12, were assigned. A thirteenth was added in 1907, and State Roads 14 to 18 in 1909.[1]

However, it was not until 1913 that a connected system was laid out—earlier state roads had been disconnected segments of road needing improvements. The seven primary roads were only assigned names, while the older state roads kept their numbers as secondary roads. In 1923, most state roads were assigned new numbers, though the primary and secondary split remained, and several roads remained named only. The United States Numbered Highways were assigned in late 1926, overlapping some of the State Roads.

The first major reworking of the system was passed in 1937, including a complete renumbering. A number of Primary State Highways were designated, while Secondary State Highways were suffixed spurs off those. For instance, Primary State Highway 1 was the Pacific Highway (present Interstate 5), and Secondary State Highway 1B was a spur from Bellingham to the Canadian border (now State Route 539). U.S. Routes kept dual designations with State Highways. By 1952, the present highway shield, in the shape of George Washington's head, had been adopted.

The primary/secondary state highway systems were replaced by the current numbering system in the 1960s. The signs for the new highway numbers first were posted in 1964, while the PSH/SSH signs were removed in 1970.

Secondary State Highways (SSH) were branches of Primary State Highways.[2]

• Branches of PSH 1
• Branches of PSH 2
• Branches of PSH 3
• Branches of PSH 4
• Branches of PSH 5
• Branches of PSH 6
• Branches of PSH 7
• Branches of PSH 8
• Branches of PSH 9
• Branches of PSH 10
• Branches of PSH 11
• Branches of PSH 12
• Branches of PSH 13
• Branches of PSH 14
• Branches of PSH 15
• Branches of PSH 16
• Branches of PSH 17
• Branches of PSH 21
• Branches of PSH 22

PSH 1 followed the route of U.S. Route 99 (now Interstate 5) from Vancouver to Blaine. It also served U.S. Route 99 Alternate (now SR 11) in Skagit and Whatcom counties.

This route followed the route of U.S. Route 10 (now Interstate 90) from Seattle to near Ellensburg, then U.S. Route 97 to Peshastin, then U.S. Route 2 to Spokane, then US 10/I-90 from Spokane to the Idaho state line. A southern branch of PSH 2 followed the route of Washington State Route 18 from Snoqualmie to Tacoma.

This route followed Interstate 82 from Ellensburg to the Oregon State line (concurrent with U.S. Route 97 from Ellensburg to Union Gap and U.S. Route 410/12 from Union Gap to the Tri-Cities), U.S. Route 410 (now U.S. Route 12) from the Tri-Cities to Clarkston, U.S. Route 195 from Clarkston to Pullman, SR 27 from Pullman to Oaksedale, US 195 from Oakesdale to Spokane, U.S. Route 2 from Spokane to Mead and U.S. Route 395 from Mead to the U.S.-Canada border. Spurs extended along I-82/, SR 125 and SR 129 from Tri-Cities, Walla Walla and Clarkston to the Oregon State Line

This route was also known as the "Inland Empire Highway" and crossed the first, and for a time, the only highway bridge over the middle Columbia River. That bridge was located between the towns of Kennewick, WA and Pasco, WA.

This route followed State Route 30 (now part of State Route 20) from Tonasket to Republic and State Route 21 from Republic to Wilbur.

This route followed State Route 7 from Tacoma to Morton, the former State Route 14 (now U.S. Route 12) from Morton to Yakima.

The route followed present-day U.S. Route 2 from Spokane to Newport, and State Route 31 (a portion of which is now State Route 20) from Newport to the Canada-United States border

This route followed U.S. Route 10/Interstate 90 from Ellensburg to George, State Route 281 from George to Quincy, and State Route 28 from Quincy to Davenport

The route followed State Route 14 (designated as Washington State Route 12 from 1964-67) from Vancouver, Washington to Maryhill, U.S. Route 97 from Maryhill to Toppenish and State Route 22 from Toppenish to Buena.

This route followed U.S. Route 101 from Olympia to Aberdeen.

This route ran on U.S. Route 97 from the U.S.-Canada border to Wenatchee, and State Route 28 from Wenatchee to Quincy. A spur extended along State Route 17 from Brewster to Coulee City

This route followed U.S. Route 395 from Pasco to Ritzville and U.S. Route 10/Interstate 90 from Ritzville to Spokane

This route followed State Route 6 from Chehalis to Raymond, and U.S. Route 101 from Raymond to Johnsons Landing, and State Route 4 from Johnsons Landing to Kelso.

This route followed U.S. Route 101 in Washington from Aberdeen to Raymond.

This route followed State Route 16 from Hoodsport to Tacoma

This route followed U.S. Route 2 from Everett to Peshastin

This route followed State Route 20 from Fredonia to Pateros, and State Route 153 from Pateros to Twisp

The route followed the route of U.S. Route 10 (now Interstate 90) from George to Ritzville

Primary State Highway No. 21, Tidewater Creek to Bremerton Section, 1941

The route followed present-day State Route 104 from the Kingston Ferry to the Hood Canal Bridge, then State Route 3 from the Hood Canal Bridge to Belfair, then State Route 106 from Belfair to Skokomish

The route is co-terminus with present-day Washington State Route 25.