SR 104 starts at Jct US 101 a few miles south of Discovery Bay. From US 101, SR 104 heads east, crossing Hood Canal on the W. A. Bugge Hood Canal Floating Bridge. The floating bridge replaces a ferry route that connected South Point and Lofall. From the east end of the bridge, SR 104 continues east to Kingston, where SR 104 crosses Puget Sound to Edmonds via the Edmonds-Kingston ferry route. From the Edmonds ferry pier, SR 104 heads SE to the Snohomish-King County line. Most of the way from SR 99 to the I-5 interchange, SR 104 straddles the county line, with the eastbound lanes in King County and the westbound lanes in Snohomish County. East of I-5, SR 104 heads SE to Jct SR 522 in Lake Forest Park, where SR 104 ends. SR 104 is 31.75 miles long.
Before 1964, SR 104 from US 101 to the first intersection east of the Hood Canal Floating Bridge was SSH 9E;from Jct SSH 9E to Kingston, part of PSH 21; from Edmonds to US 99, part of SSH 1W; and from US 99 to Lake Forest Park, SSH 2B.
Primary State Hwys Secondary State Hwys