1 Line (Sound Transit)

The 1Line, formerly Central Link, is a light rail line in Seattle, Washington, United States, and part of Sound Transit's Link light rail system. It serves 26 stations in King and Snohomish counties, traveling 41 miles (66 km) between Lynnwood City Center and Federal Way Downtown stations. The line connects Lynnwood, Mountlake Terrace, Shoreline, the University District, Downtown Seattle, the Rainier Valley, Seattle–Tacoma International Airport, Kent, Des Moines, and Federal Way. The 1Line carried over 35.5million total passengers in 2025, with an average of nearly 103,000 daily passengers on weekdays. It runs for 20 hours per day on weekdays and Saturdays, with headways as low as six minutes during peak hours, and reduced 18-hour service on Sundays and holidays.

Trains are typically composed of three or four cars that each can carry 194 passengers, including 74 in seats, along with wheelchairs and bicycles. Fares are paid through the regional ORCA card, paper tickets, or a mobile app. Sound Transit uses proof-of-payment to verify passenger fares, employing fare ambassadors and transit police to conduct random inspections. Until August 2024, fares were calculated based on distance traveled. All stations have ticket vending machines, public art, bicycle parking, and bus connections, while several also have park-and-ride lots. Stations between Lynnwood and Seattle are shared with the 2Line, which serves the Eastside region of King County.

Voters approved Central Link in a 1996 ballot measure and construction began in 2003, after the project was reorganized under a new budget and truncated route in response to higher than expected costs. The light rail line, which followed decades of failed transit plans for the Seattle region, opened on July 18, 2009, terminating at Westlake in the Downtown Seattle Transit Tunnel and Tukwila International Boulevard near Sea–Tac Airport. It was extended south to SeaTac/Airport in December 2009, north to the University of Washington in March 2016, and south to Angle Lake in September 2016. The line was temporarily renamed the Red Line until its designation was changed to the 1Line in 2021, coinciding with an extension to Northgate.

The first cross-county extension, north to Lynnwood, opened in August 2024; it was followed by a southern extension to Federal Way that opened in December 2025. The 2Line began interlined service with the 1Line between Lynnwood and Downtown Seattle in February 2026 and fully opened a month later. Further expansion under Sound Transit 3 is planned to divide the current corridor between two lines, the 1Line from Ballard (via the Ballard Link Extension) to Tacoma and the 3Line from Everett to West Seattle.