Seattle was U.S. Route 10's western terminus until 1969. It entered Seattle via the Lacey V. Murrow Memorial Bridge (which now carries eastbound Interstate 90) and became the long since scrapped Lakeway Expressway. Lake Way ended at Rainier Avenue and U.S. Route 10 followed it north to Dearborn Street, which carried U.S. Route 10 to Airport Way (now Seattle Boulevard) which U.S. Route 10 followed north and ended at Fourth Avenue (which was then U.S. Route 99). After 1969, Lake Way and U.S. Route 10 were replaced by Interstate 90, which ends at State Route 519 (Edgar Martinez Drive) next to Safeco Field.
The earlier routing of U.S. Route 10 followed Rainier Avenue and Martin Luther King Jr. Boulevard out of Seattle and went around Lake Washington through Renton. Today State Route 900 uses much of this routing. In 1940, the new Lakeway Expressway was built between Issaquah and Rainier Avenue in Seattle which included the Lacey V. Murrow Memorial Bridge. U.S. Route 10 now had a more direct routing into Seattle which attracted tourism due to the floating bridge segment. Today, pieces of Lakeway are still visible from Interstate 90, including part of the original tunnel in eastern Seattle and segments of the Lacey V. Murrow Memorial Bridge.
U.S. Routes 99, 10 and 410 were the only three U.S. Highways that either existed or were planned to exist within Seattle's city limits.