the Washington and Alexandria Railroad was the rail link between Long Bridge and Alexandria
Source: Library of Congress, Plan of the city of Washington : the capitol [sic] of the United States of America (by S. Augustus Mitchell, 1874)`
the 1945 topographic map shows the Richmond, Fredercksburg and Potomac (RF&P) Railroad between Potomac Yard and Long Bridge
Source: US Geological Survey, Alexandria, VA 1:31,680 scale topographic quadrangle (1945)