Primary State Highway 15-Cascade Highway

PSH 15 (Trunk)

PSH 15 was a relatively late addition to the Primary State Highway system. It was added by the 1931 legislature. PSH 15 began at Jct PSH 1 (US 99) in Everett and headed via Cavaleros Corner and Snohomish to Jct PSH 15 BM at Monroe. The Everett to Cavaleros Corner portion of PSH 15 had originally been part of PSH 1. From Monroe, PSH 15 climbed along the Skykomish River to Stevens Pass. Heading downhill via Leavenworth, PSH 15 ended at Jct PSH 2 (US 97 and, at the time, US 10) near Peshastin. In 1940, PSH 15 was resigned as Alt US 10. In 1948, the Alt US 10 designation was replaced by US 2, the number still posted today.

Planned in the 1940s and built in stages between 1960-1964, PSH 15 BM headed NE from the Bothell-Woodinville area to Jct PSH 15 at Monroe. When the current state highway numbering system was first posted in 1964, PSH 15 was designated SR 202. In 1970, the SR 522 designation from Woodinville to North Bend was swapped with the SR 202 designation from Woodinville to Monroe. SR 522 from Seattle to Woodinville remains SR 522.