The Dalgren Railroad was built by the U.S. Navy in 1942 to transport castings from the Washington Navy Yard in Washington D.C. to the weapons testing facility at Dahlgren.  It was constructed to enable year-round transport, since freezing of the Potomac River hindered winter barge traffic. The line extended from Dahlgren Junction with the Richmond, Fredericksburg and Potomac (RF&P) Railroad, now the CSX, to the Dahlgren Naval Support Facility.  The line was operated by the Navy from 1942 to 1957.  It sat unused for many years until it was sold in 1965.  The western portion of the line remains as an operating track, while the eastern portion has been made into the Dahlgren Heritage Trail.