First Avenue South Bridge

The First Avenue South Bridge is a bascule bridge with two movable leaf spans crossing the Duwamish River south of Seattle. The structure carries State Route 99 traffic and features two symmetrical hinged sections that lift to allow river traffic to pass underneath.

The original northbound span opened in 1956 and linked industrial areas with residential neighborhoods to the south and southwest. Between 1996 and 1998 a major overhaul modernized the lifting mechanism and completely rebuilt the approach roads.

The bridge functions as a central transportation artery in Seattle, influencing the development of surrounding industrial and residential communities over multiple generations.

Vessels can pass through when the bridge opens, a process lasting about four minutes supervised by the US Coast Guard 13th District. The openings follow federal navigation rules, so travelers may occasionally experience traffic pauses.

The bridge regularly lifts to allow larger vessels to pass through, a dramatic sight that interrupts everyday traffic in an urban setting. These openings remind drivers that the roadway must share space with river navigation.

Location: Seattle

Inception: 1956

Official opening: 1956

GPS coordinates: 47.54220,-122.33400

Latest update: December 12, 2025 17:45