US 99 (trunk)
US 99 was part of the original US Highway System adopted in 1926. The Washington State portion ran from the Interstate Bridge at the Oregon-Washington state line to Blaine at the British Columbia Canada-Washington State USA boundary. US 99 was decomissioned in Washington State in 1969. I-5 replaces US 99 as the main north-south highway in Washington State. Click here to see a detailed description of the US 99 trunk.
Alt US 99 Seattle
When the first phase of the Alaskan Way Viaduct in Seattle was opened to traffic in the early 1950s, it was designated as Alt US 99. By the late 1950s it had been redesignated as Bypass US 99.
Alt US 99 Burlington to Bellingham
When the US 99 trunk route was moved from Chuckanut Drive to the route via Alger in the mid 1930s, Chuckanut Drive became Alt US 99. In 1964, Chuckanut Drive was renumbered SR 11.
Alt US 99 Bellingham-Lynden-Canadian Border
Alt US 99 from Bellingham via Lynden to the Canadian border was added to the US highway system in 1954. This route was dropped as a US highway in 1969 and is now SR 539.
Before 1964, this route had been SSH 1B.Business US 99
When the Alaskan Way Viaduct was built in the 1950s, former US 99 through the heart of Downtown Seattle was designated Business US 99. This designation was dropped sometime in the 1960s.
Bypass US 99
The Alaskan Way Viaduct route was changed from Alt US 99 to Bypass US 99 in the late 1950s. In the early 1960s, this route became just plain US 99. Since 1969, the viaduct has been part of SR 99.
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