The Alaskan Way Viaduct carried State Route 99 2.1 miles along the Elliot
Bay waterfront. While the waterfront was primarily industrial when the viaduct
was constructed, interest in making the post-industrial waterfront more
accessible, along with damage from an earthquake in 2001 and vulnerability to
future earthquake damage led to interest in removing the aging structure. The
viaduct was replaced by a $4.25 billion tunnel in 2019.