[2] In 1959, the study's final report included two rapid transit lines that anticipated downtown Washington subways.

With the formation of WMATA in October 1966, planning of the system shifted from federal hands to a regional body with representatives of Washington, D.C., Maryland, and Virginia.

[6] Instead, routes had to serve each local suburban jurisdiction to assure that they would approve bond referendums to finance the system.

[9][10][better source needed] The railroad's predecessor, the Washington Southern Railway, constructed the section in 1896 within the grade of the old disused Alexandria Canal.

[10][11] In March 1968, the WMATA board approved its 98-mile (158 km) Adopted Regional System (ARS), which included the Blue Line from Huntington to Addison Road, with a possible extension to Largo.

[14] Service on the Blue Line began on July 1, 1977, on 18 stations between National Airport in Crystal City and Stadium–Armory in Washington, the first link of the Metro to Virginia.

[24] From 1999 to 2008, the Blue Line operated to Huntington on July 4, as part of Metro's special Independence Day service pattern.

[16] By the time the extension opened in 2004, professional basketball and hockey had relocated to a new arena atop the Gallery Place station, and the Capital Centre was replaced with a shopping mall.

Additionally, trains operated to Huntington between December 20, 2020, and January 3, 2021, due to a complete closure at Alexandria Rail Yard.

On December 14, 2020, WMATA announced that Blue Line service will be suspended between February 13 to May 23, 2021, to rebuild the platforms at both Arlington Cemetery and Addison Road.

[42][43] The Yellow Line resumed service on this date, but with its northeastern terminus truncated from Greenbelt to Mount Vernon Square.

[16] The Federal Transit Administration, in cooperation with WMATA, the National Park Service and The City of Alexandria government, completed an environmental impact statement for the project in June 2016.

[46] The southwestern terminal of the Blue Line is the Franconia–Springfield located at the intersection of Frontier Drive and the Franconia-Springfield Parkway (Virginia Route 289).

The joint line continues north along the CSX Railroad until it curves to the east on an elevated bridge adjacent to the National Airport terminal.

The tunnel bends south under 12th Street NW and crosses underneath the Red Line at the Metro Center station.

The tunnel then turns east under D Street SW, passing under the Green and Yellow Lines at the L'Enfant Plaza station.

[52] A second improvement project involves building a pedestrian tunnel to interconnect the Gallery Place station with Metro Center.

[53] In addition, a transportation planning group has proposed an extension of the Blue Line that would reach Potomac Mills in Prince William County.