Alaskan Way Viaduct Legacy Part 2; the Alaskan Way Viaduct and the history of US Route 99 in downtown Seattle
The Alaskan Way Viaduct was a double-decked freeway structure which once lined the Seattle Waterfront. The viaduct structure was constructed in segments between 1949-1959 as a limited access bypass realignment of US Route 99 in downtown Seattle. During 1969 the structure would become part of Washington State Route 99 when US Route 99 was eliminated in Washington State. The structure would persist for several decades and was ultimately damaged by the 2001 Nisqually Earthquake.
Part 2 of this series features the history of the Alaskan Way Viaduct and alignment history of US Route in downtown Seattle. The blog cover is from the Columbia Street on-ramp to the northbound viaduct structure. This was the last ramp completed along the Alaskan Way Viaduct in 1966 and ultimately was the last known US Route 99 shield posted in Washington.
This blog is part of the larger Gribblenation US Route 99 Page. For more information pertaining to the other various segments of US Route 99 and its three-digit child routes check out the link the below.
Part 1 of the Alaskan Way Viaduct Legacy series featured the history of Railroad Avenue:
Part 2A; the history of the Alaskan Way Viaduct and US Route 99 in downtown Seattle
In 1913 the Pacific Highway was established as an organized Auto Trail Association borne out of the Good Roads movement. Said Auto Trail was founded by Sam Hill who acted as the President of the Pacific Highway Association. The purpose of the Auto Trail was to create a singular Sign Route between San Diego, California north to Vancouver, British Columbia.
Within Washington the Pacific Highway was codified as a State Highway by way of 1913 Legislative Chapter 65. As legislatively defined the Pacific Highway was designated to pass through the city of Seattle. The Pacific Highway passed through downtown Seattle via the numerous local streets including partially along Railroad Avenue.
The Pacific Highway was designated as Primary State Highway 1 by way of 1923 Legislative Chapter 185.
The Pacific Highway (4), Evergreen National Highway (5) and National Parks Highway (3) can be seen using Primary State Highway 1 north of downtown Seattle on the 1925 Rand McNally map of Oregon, Washington and British Columbia. The Pacific Highway and Evergreen National Highway can be seen splitting from the National Parks Highway via Primary State Highway 1 north of Seattle at Bothell. The map does not display enough detail to clearly convey the alignment of the Pacific Highway through downtown Seattle.
The US Route System was formally approved by the American Association of State Highway Engineers (AASHO) on November 11, 1926. which formally brought US Route 99 into existence. US Route 99 overlaid the existing Pacific Highway (in Washington) and Primary State Highway 1. The description of US Route 99 can be seen on the November 11, 1926, AASHO descriptions of the US Routes in Washington State.
US Route 99 initially inherited the alignment of the Pacific Highway and can be seen passing through downtown Seattle on the 1927 Rand McNally Map of Washington State.
The 1930 Gallup map of Seattle (courtesy Dale Sanderson of usends.com) is one of the most detailed to display the earlier alignment of US Route 99 through Seattle. The northbound highway can be seen following Railroad Avenue towards the vicinity of Jackson Street in downtown. North of Jackson Street the highway appears to shift towards 1st Avenue. It is likely US Route 99 followed a jog on Pine Street and 8th Avenue to reach Howell Street. The highway originally departed downtown via Howell Street and Eastlake Avenue towards the University Bridge at Lake Union.
On June 30, 1930, the Seattle city council would approve construction of Aurora Avenue (originally Truck Avenue) through Woodward Park south to Fremont and the site of the Aurora Bridge. The incomplete footings for the Aurora Bridge appear in the October 1, 1930, Lewis Monitor. The bridge had broken ground during late 1929.
The deck of the Aurora Bridge was constructed mostly during 1931. The completed structure would be dedicated on February 22, 1932, which aligned with the 200th birthday of George Washington. From the outset the span has always been officially named as the "George Washington Memorial Bridge." The dedication ceremony can be seen in the February 25, 1932, Seattle Post Intelligencer.
By 1934 US Route 99 south of downtown Seattle had been realigned on a direct link between Marginal Way and 4th Avenue. This straightening can be seen on the 1934 Washington Department of Highways map.
This unique sign was present along 4th Avenue displayed a US Route 99 shield along with 1939 and 1940 Seattle traffic fatality statistics. A more conventional embossed US Route 99 shield can be seen on the left.
At the June 1940 AASHO Meeting the committee approved a northern alternate alignment for US Route 10. The northern alternate for US Route 10 crossed the Cascade Mountains via what was Washington State Road 15 over Stevens Pass to Everett. From Everett US Route 10 Alternate followed Hewitt Avenue, Broadway to US Route 99 at Everett Avenue. US Route 10 Alternate followed US Route 99 southbound from Everett into downtown Seattle where it met the mainline of US Route 10 at 4th Avenue and Dearborn Street. Originally the mainline of US Route 10 met US Route 99 via Jackson Street.
During the December 1946 AASHO Meeting the committee approved a request to extend US Route 2 from Bonners Ferry, Idaho to Everett. The extension of US Route 2 would replace US Route 10 Alternate over Stevens Pass and terminate at US Route 99 in Everett. US Route 10 Alternate was subsequently deleted following the extension of US Route 2.
The April 10, 1910, Seattle Times reported on a city proposal by Gould & Champney to build an elevated roadway over what was then Railroad Avenue. The proposal had the elevated road reserved for automotive and pedestrian access whereas the lower parts would be reserved for freight. The concept was passed over. As noted in Part 1; Railroad Avenue would become Alaskan Way following completion of a seawall on the Seattle Waterfront in 1936.
During the 1930s through much of World War II there was an increasing series of complaints regarding traffic on Alaskan Way and US Route 99 in downtown Seattle. In 1945 as the war was drawing to a close the city of Seattle sought projects to earmark for near-future infrastructure improvements. A bypass routing for US Route 99 in downtown Seattle was studied during 1945 via provisions of the 1944 Federal Aid Highway Act. The study recommended the development of two freeways around downtown Seattle.
During May 1947 representatives from Washington Department of Highways and United States Public Roads Administration met. It was during this meeting that the general design of the double-decker elevated Alaska Way Viaduct was finalized. These finalized plans were subsequently reviewed and approved by the Seattle city council during June 1947.
The Alaskan Way Viaduct was contentious politically for numerous reasons. The design included much debate of the placement of on/off ramps in the downtown area. Construction of the Alaskan Way Viaduct would ultimately break ground on February 6, 1950. The initial segment of the project included the viaduct structure north of Pike Street and the Battery Street Tunnel to Aurora Avenue. This segment would open to traffic following a dedication ceremony held on April 4, 1953.
The below photo is from a ventilation test in the Battery Street Tunnel conducted on July 16, 1954 (Seattle Municipal Archives).
Initially traffic heading northbound could enter the Alaskan Way Viaduct could do so via Elliott Avenue. Southbound traffic branched from Aurora Avenue at the Battery Street Tunnel. Southbound traffic entered the Alaskan Way Viaduct at the southern tunnel portal and emptied onto city streets via 1st Avenue. This alignment is shown as part of US Route 99 Alternate on the 1954 Washington Department of Highways map. US Route 99 Alternate followed 1st Avenue south of the initial viaduct structure through downtown and merged into mainline US Route 99 at 4th Avenue via Marginal Way.
On June 29, 1956, the Federal Highway Aid Act of 1956 was signed into law on the Federal Level. The Federal Highway Aid Act of 1956 was the genesis point of the Interstate Highway System which would in the coming decade sew the demise via of US Route 99 in Washington via replacement by Interstate 5.
By 1956 a segment of the Alaskan Way Viaduct had been constructed in the vicinity of Connecticut Street (now Royal Brougham Way). The viaduct structure was built as far south as Holgate Street and continued at-grade to Hanford Street. These segments would open to traffic on September 3, 1959.
The nearly complete Alaskan Way Viaduct can be seen snaking along the Seattle Waterfront during February 1958 (Seattle Municipal Archives).
Following the completion of the Alaskan Way Viaduct the surface routing of US Route 99 in downtown Seattle was eliminated. US Route 99 Alternate was subsequently repurposed as the then new mainline highway. The 1962 Washington Department of Highways map depicts US Route 99 bypassing downtown Seattle via the Alaskan Way Viaduct.
Not all the planned ramps on the Alaskan Way Viaduct were ultimately constructed. The last to be built was the Columbia Street ramp. Said ramp had been funded by the Seattle city council during September 1964 and was opened to traffic on February 1, 1966.
On June 24, 1969, the AASHO Executive Commitee approved a request by the Washington State Highway Commission to eliminate US Route 99 in Washington. The Washington State Highway Commission approved a motion to eliminate US Route 99 on April 22, 1969. The justification to eliminate US Route 99 in Washington State was to avoid confusion and cost associated with signing the highway concurrent on much of Interstate 5.
Washington State Route 99 is displayed passing through downtown Seattle via the Alaskan Way Viaduct on the 1970 Washington Department of Highways map.
The collapse of Interstate 880 on the Cypress Viaduct in Oakland, California during the 1989 Loma Prieta Earthquake led to concerns being raised about the seismic stability of the Alaskan Way Viaduct. Unlike the Cypress Viaduct the Alaskan Way Viaduct had been constructed in sections. This sectional design was thought to have been more resistant to earthquake damage.
As the Washington Office of Urban Mobility was preparing to study the Alaskan Way Viaduct the structure was impacted by the 6.8 magnitude Nisqually Earthquake on February 28, 2001. The structure was found to have shifted considerably and was subject to numerous closures while it was repaired. The viaduct was found to have subsided by 5.5 inches near Yesler Way during a 2009 engineering study.
Numerous options for replacing the Alaskan Way Viaduct were explored following the Nisqually Earthquake. This ultimately led into the Alaskan Way Viaduct replacement project which will be covered in Part 3 of this series:
Alaskan Way Viaduct Legacy Part 3; the Alaskan Way Viaduct replacement tunnel (coming soon).
Part 2B; exploring the Alaskan Way Viaduct
These photos of the Seattle Waterfront were taken by Gribblenation's Tom during May 2018. The Alaskan Way Viaduct is easily observed from the Bremerton-Seattle Ferry (Washington State Route 304).
This view is facing east towards the Alaskan Way Viaduct while departing the Bremerton-Seattle Ferry at Coleman Dock.
These photos are facing west towards the Columbia Street on-ramp to the Alaskan Way Viaduct. The last known US Route 99 shield in Washington can be seen on the overhead gantry.
These photos follow the final descent on Columbia Street to Alaskan Way. The substructure of the Alaskan Way Viaduct at the time covered Alaskan Way.
Facing towards Alaskan Way Viaduct from Union Street.
This view from 1st Avenue faces towards the Seneca Street exit from the Alaskan Way Viaduct.
The Alaskan Way Viaduct from the Harbor Step.
The Seneca Street exit from the Alaskan Way Viaduct.
This older Washington State Route 99 shield directed traffic to the Alaskan Way Viaduct on 1st Avenue.
These photos feature a drive on the southbound Alaskan Way Viaduct as it was in 2018. These photos were also taken by Gribblenation's Tom. Approaching the Battery Street tunnel on southbound Washington State Route 99 there was one final opportunity for traffic to exit into downtown onto Denny Way.
Entering the Battery Street Tunnel.
As Washington State Route 99 departed the Battery Street Tunnel it entered the Alaskan Way Viaduct structure. Both the southbound and northbound lanes initially followed each other.
The same view facing south of the Battery Street Tunnel portal standing from 1st Avenue.
The southbound lanes of the Alaskan Way Viaduct dipped below the northbound.
The southbound lanes of the Alaskan Way Viaduct had no exits into downtown. Exits could be found at Royal Brougham Way and Atlantic Street.
Ferry Traffic along Alaskan Way Viaduct was directed to exit onto Royal Brougham Way.
Royal Brougham Way also provided access to what was Safeco Field and CenturyLink Field.
In 2018 the southbound lanes of the Alaskan Way Viaduct descended a temporary structure to a surface grade. This was necessary due to part of the viaduct structure having been demolished. Then under construction Alaskan Way Viaduct tunnel replacement portal can be seen in the second photo on the right.
The Atlantic Street exit was signed as part of Washington State Route 519. This exit permitted access to Interstate 5, Interstate 90 and Coleman Dock.
This view is facing north along Railroad Way towards the Alaskan Way Viaduct.
These photos are of the seawall present underneath Alaskan Way and the Alaskan Way Viaduct.
Version History
- First published on 5/12/2018.
- First updated on 9/11/2025.
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