The Metro system opened in 1976 with five stations on the Red Line. With the Silver Line, it has 91 stations on six lines. Here is an animated slideshow of Metro’s evolution over 38 years.
This slideshow is no longer available, but you can see an updated one here.
Most of this data comes from the nycsubway.org timeline of the Washington Metro and WMATA’s history page. The dates of station name changes come from Wikipedia’s pages on individual stations and other online sources. To keep the number of maps manageable, and because many stations’ exact renaming dates are not available, station renamings are grouped with the next major service change, even when that takes place years later. For example, WMATA renamed Ballston to Ballston-MU in 1995, but the next map, showing the Green Line Commuter Shortcut, depicts the system in 1997.
From November 20, 1978 to November 30, 1979, and then again from November 22, 1980 to April 29, 1983, some Blue and Orange trains used one color going in one direction, then switched colors heading back. If you lived in Clarendon in 1981, you would board a Blue Line train headed to DC and then catch an Orange Line train to get home.
Metro had to do this in 1978-1979 because trains at the time used physical rollsigns with text printed on a colored background. The New Carrollton sign had an orange background, while the National Airport destination sign used blue. Therefore, the trains had to switch colors for each direction.
Then, in the early 1980s, this started again after the segment to Addison Road opened. At the time, with the Yellow Line not yet built, the demand for service on the Rosslyn to National Airport segment (now Blue) better matched the Stadium-Armory to New Carrollton segment (now Orange), and the demand on Rosslyn to Ballston (now Orange) lined up better with Stadium-Armory to Addison Road (now Blue).
Therefore, Metro ran trains from National Airport to New Carrollton and Ballston to Addison Road. But since the rollsigns didn’t allow using the same color for each end of those services, the trains had to switch colors in each direction.
From December 11, 1993 to September 18, 1999, the Green Line had 2 unconnected segments, one from Greenbelt to Fort Totten and the other from U Street to Anacostia.
On January 27, 1997, Metro started using a single-track switch at Fort Totten to send rush hour Green Line trains from Greenbelt onto the Red Line. They ran on the Red Line tracks to Farragut North, where there is a pocket track to turn around. This “Green Line Commuter Shortcut” continued until the Green Line opened through Columbia Heights and Petworth in 1999, connecting the two sections permanently.
This was not shown on Metro maps except for a green box explaining the service. The maps in this slideshow display it using a dashed line to illustrate the service.
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