Highway 8 is part of the first automobile route built to connect the Lower Mainland to the Alberta border. Named the Southern Trans-Provincial Highway, it ran from Vancouver to Crowsnest Pass and was later designated as Route A; the route followed Kingsway and Yale Road from Vancouver to Hope, then turned north to Spences Bridge. The route then turned southeast and passed through Merritt and Princeton along present-day Highway 8 and Highway 5A before travelling east along present-day Crowsnest Highway (Highway 3) towards Osoyoos, the Kootenays, and the Alberta border. In 1941, British Columbia transitioned from lettered to numbered highways, with the Lower Mainland section of Route A becoming Highway 1 and the remainder becoming Highway 3. After the end of World War II, the provincial government began to upgrade its highway system and constructed new sections of its highways. On November 2, 1949, the Hope-Princeton Highway through Allison Pass and Sunday Summit was opened, reducing the driving distance between Hope and Princeton from approximately to .