The latest extension, from Portland to Milwaukie, was opened in 2015, while on-going improvements for the Red Line will be completed by 2024. The original 27-station, 15.1-mile (24 km) line has since been expanded to 94 stations and 59.7 miles (96.1 km) of tracks. Construction began in 1982, and service commenced between downtown Portland and Gresham on September 5, 1986.

Planning for the network's inaugural eastside segment, then referred to as the Banfield Light Rail Project, started in 1973 ahead of the cancelation of the Mount Hood Freeway project. MAX was among the first second-generation American light rail systems to be built, conceived from freeway revolts that took place in Portland in the 1970s. Due to the COVID-19 pandemic, which impacted public transit use globally, annual ridership plummeted, with only 14.8 million riders recorded in 2021. In 2019, MAX had an average daily ridership of 120,900, or 38.8 million annually.

Trains run seven days a week with headways of between 30 minutes off-peak and three minutes during rush hours. Owned and operated by TriMet, it consists of five lines that together connect the six sections of Portland the communities of Beaverton, Clackamas, Gresham, Hillsboro, Milwaukie, and Oak Grove and Portland International Airport to Portland City Center. The Metropolitan Area Express ( MAX) is a light rail system serving the Portland metropolitan area in the U.S.

Omsi 2 buses of the south