The streetcars themselves are long gone, you can find some scattered infrastructure around town if you know where to look.
The National Park Service has jurisdiction over Washington's many parks, plazas and traffic circles. They got into a nasty bureaucratic turf war with WMATA in the 1970's as Metro was being built.
Metro opened for service to great fanfare in 1976. The initial line included just five stations stretching from Farragut North to Rhode Island Avenue, and it had taken seven years to built.
The image above was part of an intriguing but strange article published in the Washington Post in 1909.
WMATA pamphlet from 1967: "SERVICE WILL BE FREQUENT. Air conditioned trains will run every two minutes at peak hours. The system will carry 281 million riders by 1990."