- Baltimore & Ohio (now CSX)
- Cheseapeake & Ohio [via Southern trackage rights] (now CSX)
- Richmond, Fredericksburg, and Potomac (now CSX)
- Southern Railway (now NS)
- Washington and Old Dominion (abandoned)
- Washington, Baltimore, and Annapolis (abandoned)
- East Washington Railway (abandoned)
- Chesapeake Beach Railway (abandoned)
- Atlantic Coast Line [via RF&P] (now CSX)
- Seaboard Air Line [via RF&P] (now CSX)
- Pennsylvania Railroad [successor to Baltimore & Potomac] (now Amtrak’s Northeast Corridor)
- Washington Terminal Company [rail operator for Union Station] (now Amtrak)
Other Rail Services in Washington, DC/Washington, DC Area in 1950
- Railway Express Agency
- Fruit Grower’s Express (in Alexandria)
- Pullman Company
- Potomac Yard (in Alexandria – owned jointly by the PRR, B&O, C&O, and RF&P)