Badly damaged during the Civil War, on October 11, 1870[3] an extension to the north toward Quantico was authorized at a Special meeting of the company's stockholders. The company's charter limited this branch to 10 miles, leaving it 1.7 miles short of the Alexandria and Fredericksburg Railroad. This split from the existing line at Brooke and ran north to Quantico, also on the Potomac. The old line to the Aquia Creek wharf was abandoned on the opening of the Quantico wharf on May 1, 1872.[4]

On the other end of the line the Alexandria and Washington Railroad was chartered on February 27, 1854 to build from the south end of the Long Bridge over the Potomac River south to Alexandria. That line opened in 1857. The railroad went bankrupt and was sold July 9, 1887, being reorganized November 23, 1887, as the Alexandria and Washington Railway. In 1873 the Baltimore and Potomac Railroad's branch over the Long Bridge opened, giving a route into Washington, D.C., over which the A&W obtained trackage rights.

Revenue freight traffic, in millions of net ton-miles

Year

Traffic

1925

438

1933

265

1944

1462

1960

819

1970

1102

Source: ICC annual reports

The Alexandria and Fredericksburg Railway was chartered February 3, 1864, to continue the line from Alexandria to Fredericksburg. It opened on July 2, 1872, only reaching Quantico, the north end of the RF&P. At Quantico the 1.7-mile (2.7 km) Potomac Railroad, chartered April 21, 1867, and opened May 1, 1872, connected the two lines. It was leased to the RF&P for 28 years from May 17, 1877. On March 31, 1890, the two companies terminating in Alexandria merged to form the Washington Southern Railway. Until November 1, 1901, it was operated by the Baltimore and Potomac Railroad and its successor the Philadelphia, Baltimore and Washington Railroad (part of the Pennsylvania Railroad system). The Potomac Railroad lease was transferred to the Washington Southern on June 30, 1904. On February 24, 1920, the Washington Southern was formally merged into the RF&P.

The Richmond-Washington Company was incorporated September 5, 1901 as a holding company, owning the entire capital stock of the two railroads. The stock of the company was owned equally by the Pennsylvania Railroad, Baltimore and Ohio Railroad, Atlantic Coast Line Railroad, Southern Railway, Seaboard Air Line Railway and Chesapeake and Ohio Railway. Four of these companies (B&O, ACL, SAL, C&O) have since become part of CSX. The Southern Railway is now part of Norfolk Southern and does not use the former RF&P; the former Pennsylvania Railroad, in its later incarnation as Conrail, has been split between CSX and Norfolk Southern with most of PRR's routes becoming part of Norfolk Southern. However, the portion of the former PRR that connected to the very north of the RF&P's former Potomac Yard, across the Long Bridge and into Washington DC, became part of CSX following the takeover of Conrail by NS and CSX.

From 1902 to 1908, major sections of the main line totalling 21 miles (34 km) were relocated. On 31 Dec 1925 RF&P operated 118 miles of road and 432 miles of track; on 31 Dec 1970 mileages were 118 and 518.

The RF&P operated comparatively few trains of its own. One was the Old Dominion, a streamliner inaugurated in 1947 between Washington and Richmond. This train used four 70-seat coaches and a cafe-parlor car, all built by American Car and Foundry.[10]