Primary State Highways were major state highways in Washington state. They were used from 1905 to 1964. The 1964 state highway renumbering

1964 state highway renumbering (Washington)

In 1963, a law was passed authorizing a new numbering for sign routes. In 1970 the legislative definitions were changed to use the sign route numbers but renamed state routes...

 changed the highway numbering in the state to consolidate and create a more organized and systematic method of numbering the highways within the state.

History

The first state road, running across the Cascade Range

Cascade Range

The Cascade Range is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, and the notable volcanoes known as the High Cascades...

 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

Washington State Route 410

State Route 410 is a long state highway that traverses Pierce, King, and Yakima counties in the U.S. state of Washington. It begins at an interchange with SR 167 in Sumner and travels southeast across the Cascade Range to a junction with U.S. Route 12 in Naches...

 and a branch of the first road to Wenatchee

Wenatchee, Washington

Wenatchee is located in North Central Washington and is the largest city and county seat of Chelan County, Washington, United States. The population within the city limits in 2010 was 31,925...

 - 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.

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

United States Numbered Highways

The system of United States Numbered Highways is an integrated system of roads and highways in the United States numbered within a nationwide grid...

 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

Interstate 5 in Washington

Interstate 5 in Washington is a highway in the U.S. state of Washington that extends from its border with Oregon to its border with Canada...

), and Secondary State Highway 1B was a spur from Bellingham

Bellingham, Washington

Bellingham is the largest city in, and the county seat of, Whatcom County in the U.S. state of Washington. It is the twelfth-largest city in the state. Situated on Bellingham Bay, Bellingham is protected by Lummi Island, Portage Island, and the Lummi Peninsula, and opens onto the Strait of Georgia...

 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

George Washington

George Washington was the dominant military and political leader of the new United States of America from 1775 to 1799. He led the American victory over Great Britain in the American Revolutionary War as commander-in-chief of the Continental Army from 1775 to 1783, and presided over the writing of...

's head, had been adopted.

The primary/secondary state highway systems was replaced by the current numbering system

State highways in Washington

In the U.S. state of Washington, the Washington State Department of Transportation maintains a network of over 7000 miles of state highways, including all Interstate and U.S. Highways that pass through the state. The system comprises 8.5% of the state's public road mileage, but carries over half...

 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

Secondary State Highways (SSH) were branches

Spur route

A spur route is a short road forming a branch from a longer, more important route . A bypass or beltway is never considered a true spur route as it typically reconnects with the major road...

 of Primary State Highways.

• 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