"[6] In March 1968, the Washington Metropolitan Area Transit Authority (WMATA) board approved its 98-mile (158 km) Adopted Regional System (ARS) which included the Green Line from Branch Avenue to Greenbelt.

[9] Riots following the death of Martin Luther King in 1968 destroyed much of the commercial district around 14th and U Streets, and planners hoped that adding a subway stop in that area would stimulate redevelopment.

[17] Obtaining approval of the District of Columbia and Prince George's County of the exact alignment of the Green Line north of U Street delayed construction.

Originally, the ARS called for the line to be placed in the median strip of the planned North Central Freeway,[17] but after that road was cancelled, the route of the replacement subway tunnel became controversial, resulting in years of expensive delays.

[20] Increasing construction costs and financing problems (caused primarily by the inability of local governments to contribute their share of Metro's funding) led WMATA to consider shifting the Green Line to a more southerly route, along Wheeler Road SE, to terminate near Rosecroft Raceway.

[21] In January 1978, a WMATA regional task force approved a Green Line route in Anacostia that followed Martin Luther King, Jr., Avenue and then Wheeler Road down to the Beltway, with a new station added near St. Elizabeths Hospital.

The other alignment dispute occurred in the Petworth section of Washington and involved whether the tunnel would go under or skirt Rock Creek Cemetery and how to go through its soft-soil burial ground (i) and the least disruptive way under New Hampshire Avenue from Georgia Avenue–Petworth to Columbia Heights.

In September 1980, D.C. City Council member Jerry A. Moore, Jr. delivered a petition containing 1,000 signatures from Anacostia residents demanding that construction on the Green Line be sped up.

in which the newspaper concluded: "The 18.86-mile (30.35 kilometer) Green Line, which some argue should have been the first built because it would serve the most disadvantaged sections of the Washington area, is last on the construction list and threatened with extinction.

[9] The Prince George's County government, however, reaffirmed in April 1981 its support for the Rosecroft Raceway terminus, and Metro promised to hold a public hearing on the issue in June 1981.

[44] Shortly thereafter, the civil rights office of the U.S. Department of Transportation sent a letter to Metro warning that the Rosecroft Raceway route could negatively impact two historically black communities nearby.

[46] Metro agreed a month later to the plan, with the provision that $90 million per year would be spent to begin work on the inner-city portion of the Green Line (the Gallery Place, Waterfront, and Navy Yard stations).

[57] Metro declined to appeal Judge Ramsey's latest ruling,[58] and the Prince George's County Council voted to reverse its earlier decision and support the original Green Line route to Branch Avenue.

[59] Frustrated by funding constraints and the court injunction, in December 1983 Metro released a proposed "final" system map that showed the Green Line terminating at the Anacostia and Mount Vernon Square stations.

First, the transit agency hired former U.S. Secretary of Transportation William T. Coleman, Jr. in December 1983 to oversee negotiations with the various entities involved with the siting of the Green Line route and seek a resolution through the U.S. district court.

[63][65] The agreement called for construction of the Green Line to Waterfront station in the summer, siting of the tunnel under the Anacostia River by June 28, and the holding of public hearings on the remaining route between July 18 and August 3.

[41][80][81] More than 1,000 people packed "raucous" public hearings for three nights in the District and Prince George's County in early September that denounced Metro and claimed that they were "becoming a victim of transportational apartheid.

[90] Prince George's County, meanwhile, had announced that its county-run buses ("The Bus") would not run to Anacostia Station, as previously promised, drawing outrage from the D.C. representatives on Metro's board.

[91] To make up the lost revenue, WMATA said that it would run only two-car trains (the shortest on the system) on the Green Line during slow periods on weekdays and evenings and on Sundays beginning in June 1992.

[94][95] When the Van Dorn Street station opened in June 1991, Metro was forced to run trains every 12 minutes during rush hour rather than every 8 due to the rail car shortage.

[100] Even though significant numbers of bus riders in Anacostia had switched to Metrorail by February 1992, WMATA nonetheless began running two- rather than four-car trains on the Green Line on Sundays and during slow periods in order to close a revenue shortfall.

[108][109] In December 1984, WMATA's Board of Directors agreed to return the Green Line to its original route, and build the Congress Heights and Southern Avenue stations.

[40] Liquid nitrogen was used to harden the ground where the inbound tunnel reached the northern side of the Anacostia River, to lessen the possibility of cave-ins due to the wet earth.

[125] After lengthy negotiations (which included state and local guarantees to pay for cost overruns or funding shortfalls, penalties for defaults, and the imposition of two external financial monitors) and heavy pressure from Congress, Reagan administration officials released the $400 million on July 16, 1986.

[135] By mid-1991, however, falling inflation had reduced WMATA's construction costs so much that the agency said it could build the two final Green Line stations in Prince George's County without asking Congress for additional money.

[141] The funding impasse was broken in November 1991 when local and state governments agreed to roughly triple their contribution to Metro's construction costs by 1994 to complete the entire system.

[146] In August 1990, WMATA hired the Perini Corp. as the new contractor, and required the company to finish the job and rebuild the streets in the area, setting a new Green Line dedication of December 1991.

In June 1991, WMATA discovered that the District of Columbia had dumped 426,000 tons[142] of possibly hazardous incinerator bottom ash in an unused exposed culvert along the subway's potential path near St. Elizabeth's Hospital between 1977 and 1989.

[138][157] In an initial report in June 1991, WMATA determined that ash posed no environmental risk,[157] although there were concerns that the level of pollutants would prevent any excavated material from being accepted by landfills in D.C., Maryland, or Virginia.

The Green Line runs east through Fort Circle Park and tunnels under Queens Chapel Road (Maryland Route 500) to emerge along the Baltimore and Ohio Railroad right of way to Greenbelt adjacent to the Capital Beltway.