MAX Blue Line

The MAX Blue Line is a light rail service in Portland, Oregon, United States, operated by TriMet as part of the MAX Light Rail system. It travels east–west for approximately 33 miles (53 km)—the longest in the network—between Hillsboro, Beaverton, Portland, and Gresham and serves 48 stations from Hatfield Government Center to Cleveland Avenue. The line carried an average 55,370 riders each day on weekdays in September 2018, the busiest of the five MAX lines. It runs for 221⁄2 hours per day from Monday to Thursday, with headways of between 30 minutes off-peak and five minutes during rush hour. Service runs later in the evening on Fridays and Saturdays and ends earlier on Sundays.

The success of local freeway revolts in Portland in the early 1970s led to a reallocation of federal assistance funds from the proposed Mount Hood Freeway and Interstate 505 (I-505) projects to mass transit. Among various proposals, local governments approved the construction of a light rail line between Gresham and Portland in 1978. Referred to as the Banfield Light Rail Project during planning and construction as a part of the Banfield Freeway redevelopment, construction of what is now the Eastside MAX segment began in 1983. The line was inaugurated as the Metropolitan Area Express (MAX) on September 5, 1986.

Planning for a subsequent extension of MAX to the west side began as early as 1979. This second segment, known as the Westside MAX, was delayed by nearly a decade due to funding disagreements. Originally designed to terminate at 185th Avenue near the border between Hillsboro and Beaverton, proponents for a longer line achieved a supplemental extension to downtown Hillsboro just before the project's groundbreaking in 1993. The Westside MAX opened in two phases following delays in tunnel construction; the first section up to Goose Hollow opened in 1997 while the rest opened on September 12, 1998.

In 2000, the two distinct segments, already operating as a single through route between Gresham and Hillsboro, were unified in passenger information as the Blue Line after TriMet introduced a color coding scheme in preparation for the opening of the Red Line to Portland International Airport. The Blue Line currently shares its route with the Red Line on the west side, between Beaverton Transit Center and Rose Quarter Transit Center. On the east side, it shares tracks with both the Red Line and the Green Line, between Rose Quarter Transit Center and Gateway/Northeast 99th Avenue Transit Center.