The system is largely linear in a north–south direction, with one terminus near Pittsburgh's central business district and two termini in the South Hills.

The T is one of the surviving first-generation streetcar systems in North America, with the oldest portions of the network dating back to 1903 and the Pittsburgh Railways.

In 1964 the system was acquired by the Port Authority of Allegheny County, which rapidly converted most routes to buses.

Community opposition rallied against the plan and in favor of retaining the electric rail trolley system and upgrading it into modern LRT.

[6] Rail lines (trolleys) had been a staple of the city and region since the late 19th century, the idea of a downtown to Oakland or East Liberty subway had been considered since at least the 1910s.

[14] In the 1960s a 92-mile (148 km) automated guideway transit system was planned fanning out to the north, south, east, southeast and west, including connections to both the Pittsburgh International Airport and the Allegheny County Airport, Monroeville Mall and adjacent to Kennywood Amusement Park.

[citation needed] PRT, working with community representatives and government officials, undertook a detailed study on the future of the South Hills trolley lines, resolving to transform these valuable, high-density transit corridors into a modern LRT system.

The resulting Stage I LRT plan achieved a comprehensive reconstruction and upgrading of the 10.5-mile (16.9 km) "main line" between downtown and the suburbs of Bethel Park and Upper St. Clair via Mt.

The crowning achievement was to be a 1.1-mile (1.8 km) downtown subway, eliminating the trolleys' slow, street-running loop through Pittsburgh's Golden Triangle.

Stage One began with two construction projects, the downtown subway and the former trolley route from the newly constructed South Hills Village Station and Light Rail Maintenance Center to Castle Shannon, both ends working toward the middle section of the route.

The first modern light rail cars began operation from South Hills Village to Castle Shannon on April 15, 1984.

[16] The last leg of the modern suburban "Beechview" line (from Castle Shannon to South Hills Junction via Mt.

The Beechview line was reconstructed (being completely double-tracked) and routed from the South Hills Junction through the Mount Washington Transit Tunnel, emerging at a newly constructed station at Station Square before crossing the Monongahela River on the Panhandle Bridge (a former railway bridge), which then led into a newly built downtown (cut and cover tunnel) subway with four stations, which incorporated the nineteenth-century Pittsburgh & Steubenville Extension Railroad Tunnel.

The reconstruction of this line would be part of the Stage II project, to be performed at a future date pending additional funding.

Coinciding with the opening, Pittsburgh Regional Transit purchased 28 additional light rail cars to support the line and increase overall system capacity.

In addition, as part of the Stage II project, upgrades to the traction power network, Operations Control Center, and signals and communications had been implemented.

The North Side station serves PNC Park, the Andy Warhol Museum, Allegheny Center and numerous office buildings in the vicinity.

Then, from January to March 2025, portions of the downtown subway were closed for the rebuilding of the concrete beams, known as plinths, that support the light rail tracks.

Between January and February, the light rail lines were truncated to First Avenue to enable the plinths between there and Steel Plaza to be rebuilt.

[29] Pittsburgh Regional Transit operates a fleet of 83 LRVs as of 2006: Trains are generally run in a two-car configuration.

These PCCs were from an original fleet of 12 "homebuilt" cars constructed in the 1980s in the PRT shops using a combination of new underframes, lower body panels, front and rear ends, interiors, wiring and controls, together with reconditioned components such as trucks, motors, and upper body parts and windows reused from original Pittsburgh PCCs numbered in the 1700 series.

Six stops serve Upper St. Clair and Bethel Park before merging with the Blue Line at Washington Junction.

The line then makes eight well-spaced stops on its arc through the Overbrook, Brookline, Carrick, Beltzhoover, and Bon Air neighborhoods of southern Pittsburgh.

The Blue Line–South Hills Village route follows the South Hills Village leg of the Red Line and the common leg from Washington Junction to Willow Station, which is adjacent to Overbrook Junction, where it switches to the Silver Line mainline.

In September 1999, PRT withdrew the four remaining active-service PCCs from service and closed the Drake line altogether.

[citation needed] The Brown Line, formerly 52, ran from South Hills Junction over Mount Washington and across the Monongahela River to downtown Pittsburgh, terminating at Wood Street.

As of February 2021, Pittsburgh Regional Transit's newly released 25-year plan includes the possibility of reviving service on the Allentown line due to continuing growth of the neighborhood.

Former Chief Executive of Allegheny County Dan Onorato hoped to eventually extend the light-rail system east to Oakland[38] and west to Pittsburgh International Airport.

[39] In 2009, Onorato, along with Congressman Mike Doyle, requested approximately $7 million in funding from the federal government for preliminary planning of the extension.

[40] The Pittsburgh Post-Gazette took a strong editorial stance in late 2012 for a workable extension to the northern suburbs all the way to Cranberry.