It was built between 1981 and 1984 after the previous bascule bridge was deemed inoperable as a result of being struck by the freighter Antonio Chavez in 1978.

The high-level bridge was closed in March 2020 after cracks in the underside were found to be growing rapidly, necessitating a major repair amid the COVID-19 pandemic.

[4] The bridge spans the east and west channels that form the mouth of the Duwamish River at Elliott Bay, crossing over Harbor Island.

The low-level bridge carries the surface-level Spokane Street and has a navigational clearance of 45 feet (14 meters).

A 1968 Forward Thrust ballot measure included $16.7 million in funding for the bridge, largely to receive votes from West Seattle residents.

Despite the 68 percent support in the 1968 ballot measure, the state withdrew its urban streets money due to the scandal.

Tiemann also quipped, "Short of a tug knocking it down (which could trigger federal special bridge replacement funds), there is nothing else.

"[9] In March 1978, several prominent West Seattle residents filed a petition to organize a secession referendum, with the hopes of finding state funding for a new bridge to serve their independent city.

[10] The secession campaign was required to gather 29,000 signatures for a ballot measure, but were unable to meet the threshold before the northern or westbound drawbridge was permanently closed[11] and all east–west traffic was funneled over the southern span.

While federal lawmakers were opposed to appropriating funds to a high-level bridge, Seattle City Council member Jeanette Williams, who served on the council from 1970 to 1989, lobbied Congress for the bridge and successfully secured funds with help from Senator Warren Magnuson.

It carries Southwest Spokane Street over the Duwamish River, connecting Harbor Island to West Seattle.

Each 7,500-short-ton (6,800 t) leaf of the bridge floats on a 100-inch (2.5 m) steel barrel in hydraulic oil, situated in center piers at each side of the river.

[20] On March 23, 2020, SDOT began a long-term closure of the bridge for emergency repairs after cracks in the deck were discovered during a routine inspection.

[23] On April 15, SDOT announced that the bridge will be closed until at least 2022 because of more extensive damage found and estimated time to complete bracing for the repair project.

[24] In November 2020, mayor Jenny Durkan announced that the city would focus on repairing the bridge for $47 million with a projected opening of 2022.

However, a series of fatalities led to recognition that the aging Spokane Street Viaduct portion was unsafe to be used as a high-speed roadway.