The square, commonly referred to as "Portland's Living Room", is situated on a 40,006-square-foot (3,716.7 m2) city block in the center of downtown.

[7] In 1969, block owner Meier & Frank requested a permit to construct an 800-car parking garage at the site,[11] which the Portland City Council rejected following a series of heated public hearings.

[12] The controversial proposal led the city and local businesses to pursue a comprehensive downtown plan that envisioned turning the site into a public space instead.

[13][14] After negotiating with Meier & Frank, the city purchased the property and in 1980, announced a national design competition for a plaza that would be called "Pioneer Courthouse Square".

Just over a year later, TriMet published a conceptual design report of the project that outlined a 27-station, 15.1-mile (24.3 km) line and included a pair of light rail stations at Pioneer Courthouse Square.

[15]: 37–38  Construction of the line commenced in April 1983 in Gresham and largely progressed from east to west,[16][17] with the downtown segment among the final sections to be completed.

[22][23] On September 5, 1986, the light rail line, which TriMet officially named the Metropolitan Area Express (MAX), opened to the public.

[24] A three-day celebration took place across the route, including at Pioneer Courthouse Square, which hosted an opening ceremony and several concerts.

[31][32] TriMet's ticket office is located inside the visitor information center on the west side of the square between the Waterfall Fountain.

[37] The Pioneer Square stations also facilitate transfers to TriMet and C-Tran buses serving the Portland Transit Mall,[37][41] including a future connection to FX–Division via stops 5th and Salmon and 6th and Taylor.