You could probably get these postcards at the information booth at Union Station back in the old days. Capital Transit was formed in 1933 with the merger of the three existing transit providers (Washington Railway, Capital Traction, and Washington Raid Transit.) Although Capital Transit closed several streetcar lines and replaced them with buses, they also updated the streetcar fleet with streamlined modern PCC streetcars. In 1945, they had the third largest streetcar fleet in the United States.
They ran into financial trouble in 1955, due in part to the owners paying themselves huge dividends during a time of declining transit ridership. They tried to make up for the falling revenue and squandered reserves by requesting a fare increase, which was denied. As a result, they were unable to offer any raises for employees and the employees went on strike. During the seven-week strike, passengers had to find other ways to travel.
Capital Transit met its demise in an interesting and unusual way. One of the owners, Louis Wolfson, dared the Senate to revoke his franchise, claiming no one else would be willing to take it over. Congress did indeed revoke his franchise, and the new system, under the leadership of Ray Chalk, was known as DC Transit.