Wikipedia:WikiProject Washington State Highways/Auto trails

California-Banff "B" Line, Oregon (Walla Walla) to Idaho (Newport) via PSH 3, PSH 6
Evergreen National Highway, Canada (Blaine) to Idaho (Clarkston) via PSH 1, PSH 8, PSH 3
George Washington National Highway, Seattle to Idaho (Coeur d'Alene) via PSH 2
Glacier Trail, Canada (Blaine) to Idaho (Newport) via PSH 1, PSH 2, PSH 6
National Park to Park Highway, Oregon (Vancouver) to Idaho (Newport) via PSH 1 (branch on PSH 5, Tacoma-Rainier), PSH 2, PSH 6
National Parks Highway (Northwest Trail), Oregon (Vancouver) to Idaho (Coeur d'Alene or Rathdrum) via PSH 1 (branch on PSH 5, Tacoma-Rainier), PSH 2
Okanogan-Cariboo Trail, Wenatchee to Canada (Oroville) via PSH 10
Pacific Highway, Oregon (Vancouver) to Canada (Blaine) via PSH 1
Theodore Roosevelt International Highway, Oregon (Walla Walla) to Idaho (Newport) via PSH 3 (Eastern Division), PSH 6
Yellowstone Trail, Seattle to Idaho (Coeur d'Alene) via PSH 2, PSH 3, PSH 2

PSH 1
- 1910: Pacific Highway Association formed
- 1913: Pacific Highway name assigned
PSH 2
- 1912: Yellowstone Trail Association formed
- 1913: Sunset Highway name assigned
- 1915: National Parks Highway Association formed
PSH 3
- 1913: Inland Empire Highway name assigned
PSH 5
- 1913: National Park Highway name assigned
- 1916: National Park-to-Park Highway Association formed
- by 1921: National Parks Highway Association extended route from Seattle to Mount Rainier
PSH 8
- 1917: Evergreen Highway Association formed
- 1937: Evergreen Highway name assigned