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.

In 1890, the first electric streetcar opened in Albina while the first cable car began serving 5th Avenue; these marked the start of an era of major rail expansion.

[10]: 61, 93 [15] At the height of local freeway revolts in the 1970s, studies for public transit began using funds made available by the Federal-Aid Highway Act of 1973.

[5]: 20  These funds had been intended for the Mount Hood Freeway and Interstate 505 (I-505) projects,[5]: 30  which were abandoned amid strong opposition from the Portland city government and neighborhood associations.

[16][17] In 1973, Governor Tom McCall assembled a task force that helped determine several alternative options, including a busway and light rail.

[18] Local jurisdictions originally favored the busway alternative but support for light rail prevailed following the mode's inclusion in a 1977 environmental impact statement.

[33] At the same time TriMet was planning the Westside MAX in the mid-1980s, Metro regional government announced new light rail proposals for Clackamas County.

[34] Further planning led JPACT to favor the I-205 corridor due to an existing right-of-way along the I-205 Transitway, an unfinished mass transit component of the freeway that had been built to accommodate a busway.

[37] In 1989, studies for both I-205 and Milwaukie proposals received funding from the U.S. Senate Committee on Appropriations under the condition that they included potential route extensions to Clark County, Washington.

[45] To move the project forward, TriMet downsized the plan and abandoned the line's Clark County and North Portland segments up to the Rose Quarter.

[48][49] The legislature met again in February 1996 and passed a revised $375 million package,[48] but light rail opponents forced a statewide vote and defeated it the following November.

[55] In 1997, engineering firm Bechtel accelerated plans by submitting an unsolicited proposal to design and build an airport rail link in exchange for 120 acres (49 ha) of Port property.

Additionally, TriMet had announced it would procure up to eight new light rail vehicles to accommodate the improvements,[92] but later purchased 30 new trains overall; four were part of A Better Red, while the remaining 26 were replacements for the original MAX fleet, which are gradually being retired.

[96] TriMet adopted a locally preferred alternative in April 2019,[97] and the FTA announced $99.99 million for the project through the Capital Investment Grants program in May 2020.

[102] From April 2–9, 2022,[103][104] Red Line service was suspended to make way for construction, and shuttle buses operated between Gateway Transit Center and Portland International Airport.

[109][110] From January 14 to March 3, 2024, TriMet suspended MAX Red, Blue and Green Line service between NE 7th and Gateway Transit Center.

[114][115] TriMet works with local jurisdictions and agencies to identify and recommend priority transit projects to include in Metro's Regional Transportation Plan (RTP).

[151][152] A three-mile (4.8 km) section of tracks runs beneath Washington Park in Portland's West Hills through the Robertson Tunnel, the system's longest underground segment.

In studies conducted for the Eastside MAX, planners recommended using the Steel Bridge due to its former role as a river crossing for the city's historic streetcars.

[4] Approximately 70 percent of the MAX system uses automatic block signaling (ABS),[4] which allows for relatively fast operating speeds—up to 55 miles per hour (89 km/h)—and short headways.

[132][156][157] For example, between Lloyd Center/Northeast 11th Avenue station and Gateway Transit Center along the Banfield Freeway, ABS can accommodate an operating headway of two minutes.

[165][166] Like other North American light rail systems,[167] MAX stations do not have faregates; paid fare zones are delineated but remain accessible to anyone.

[186][187] Stations built as part of the Banfield Light Rail Project were originally fitted with electric wayside lifts to accommodate riders with mobility devices on the system's high-floor, first-generation vehicles.

Twenty-six Type 1 high-floor vehicles were produced for the Banfield light rail project by a joint venture between Bombardier and La Brugeoise et Nivelles beginning in 1983.

[192] MAX then became the first light rail system in North America to acquire low-floor train sets when TriMet procured 39 model SD660 cars from Siemens in 1993.

[232] TriMet attributes falling ridership to perceived crime within trains and stations and lower-income riders being forced out of the inner city by rising housing prices.

[235] As is standard practice on North American light rail systems,[236] MAX uses proof-of-payment for fare collection, and stations do not have ticket barriers.

[248] On August 25, 2024, TriMet introduced four new bus routes to replace late-night MAX services, to expand the length of time available each night for routine overnight maintenance.

In September 2009, the service moved to the newly opened MAX alignment along the transit mall, running between Union Station to Portland State University,[137][258] and remained on this route in subsequent seasons.

In 2011, the service was reduced to seven or eight Sundays per year,[259] and in July 2014 it was discontinued entirely and the two remaining faux-vintage cars were sold to a group planning a streetcar line in St.