Questions of the structure's seismic vulnerability were raised after several earthquakes damaged similar freeways in other cities, including some with the same design as the viaduct.

The state and city governments considered several options, including a rebuilt elevated structure, a surface boulevard, and cut-and-cover tunnel, but could not compromise on a final choice.

A deep-bored tunnel was selected in 2009 and the southern section of the viaduct was demolished in 2011 and replaced with a six-lane, single-deck freeway that travels through the SoDo industrial area.

The Alaskan Way Viaduct was a double-decker freeway that traveled through Downtown Seattle and SoDo along the western waterfront facing Elliott Bay.

[21] The waterfront section of the viaduct was noted for its scenic views, which include Elliott Bay, the distant Olympic Mountains, and the city's skyline.

[8] Between the Seattle Aquarium and Pike Place Market, the double-decker viaduct ended as SR 99 split into a pair of side-by-side elevated lanes that traveled over the north portal of the Great Northern railroad tunnel and under Victor Steinbrueck Park.

[23][24] The Western Avenue crossing included a notch in the southbound railing of the viaduct, which was cut out to pass around a column of the Seattle Empire Laundry Building.

An elevated roadway, placed along the waterfront's Railroad Avenue (later renamed Alaskan Way), was recommended by several city engineers in the latter part of the decade.

[39] The 2001 Nisqually earthquake damaged the viaduct and its supporting Alaskan Way Seawall and required the Washington State Department of Transportation (WSDOT) to invest US$14.5 million in emergency repairs.

[40] Due to damage from continuing settlement, a group of researchers and faculty from the University of Washington urged the mayor of Seattle (in 2007) to close the viaduct within a four-year timeframe.

[44] This caused a two-year delay as it was necessary to dig a 120-foot (37 m) vertical shaft recovery pit from the surface in order to access and lift the cutterhead for repair and partial replacement.

[49] In July 2016, a citywide ballot measure attempted to build an elevated park along the waterfront after the demolition of the viaduct, utilizing a portion of the existing structure.

[52] WSDOT reverted to the tunnel's original opening date of early 2019 to accommodate a longer preparation period and avoid potential work delays due to winter weather.

On January 11, 2019, the Alaskan Way Viaduct was permanently closed in preparation for the opening of the new tunnel, which required the excavation of several buried ramps at the south portal and other road realignments.

[57] Demolition work reached the 50 percent milestone on June 11, with the Pioneer Square and Pike Place Market sections left for the final stages.

[58][59] The final double-deck section of the viaduct, including the Marion Street pedestrian bridge at Colman Dock, was demolished in late September 2019.