The Alaskan Way Viaduct, completed on April 4, 1953, is a double-decked elevated section of State Route 99 that runs along the Elliott Bay waterfront in the industrial district and downtown of Seattle. It is the smaller of the two major north–south traffic corridors through Seattle (the other being Interstate 5), carrying up to 110,000 vehicles per day. The viaduct runs above the surface street, Alaskan Way, from S. Nevada Street in the south to the entrance of Belltown's Battery Street Tunnel in the north, following previously existing railroad lines.

The viaduct was damaged in the 2001 Nisqually earthquake, and was proposed to be replaced, in part by an underground tunnel running beneath the city's downtown core.

The initial phase of demolition and removal of the viaduct began on October 21, 2011.

The 1989 Loma Prieta earthquake destroyed the similarly designed Cypress Street Viaduct in Oakland, California with considerable loss of life. 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. Experts give a 1-in-20 chance that the viaduct could be shut down by an earthquake within the next decade. Since the Nisqually Earthquake occurred, semi-annual inspections have discovered continuing settlement damage.

Alaskan Way, originally Railroad Avenue, is a street in Seattle, Washington, that runs along the Elliott Bay waterfront from just north of S. Holgate Street in the Industrial District—south of which it becomes East Marginal Way S.— to Broad Street in Belltown—north of which is Myrtle Edwards Park and the Olympic Sculpture Park. The right-of-way continues northwest through the park, just west of the BNSF Railway mainline, and the roadway picks up again for a few blocks at Smith Cove. It follows a route known in the late 19th century as the "Ram's Horn" (because of its shape). Alaskan Way gives its name to the Alaskan Way Viaduct, which carries Washington State Route 99 through Downtown Seattle.

The idea of building a rail corridor along Seattle's Central Waterfront goes back at least to Thomas Burke and Daniel Hunt Gilman and the construction of the Seattle, Lake Shore and Eastern Railway in the years before the Great Seattle Fire of 1889. Railroad Avenue was built as a planked roadway on pilings over the waters of Elliott Bay. South of Downtown, the rail line constituted the one major man-made feature in an area of tideflats.