Baltimore & Potomac Railroad

Baltimore and Potomac Rail Road
Locale	Maryland Washington, D.C.
Dates of operation	1872–1902
Successor	Philadelphia, Baltimore & Washington Railroad
Track gauge	4 ft 8 ¹⁄₂ in (1,435 mm) standard gauge
Headquarters	Philadelphia

The Baltimore and Potomac Railroad (B&P) operated from Baltimore, Maryland, southwest to Washington, D.C., from 1872 to 1902. Controlled by the Pennsylvania Railroad, it was the second railroad company to connect the nation's capital to the Northeastern States, and competed with the older Baltimore & Ohio Railroad.

Part of the B&P route is now part of Amtrak's Northeast Corridor, the most heavily traveled American intercity passenger line; and of the Penn Line of the Maryland Transit Administration's MARC commuter train service. Its Baltimore and Potomac Tunnel, bored under north Baltimore in 1871, remains in use.

The leading advocate for expanding the railroad system into southern Maryland was Walter Bowie, who wrote newspaper articles and columns under the pen name Patuxent Planter and who joined Thomas Fielder Bowie, William Duckett Bowie, and Oden Bowie (later Governor of Maryland), in lobbying the Maryland General Assembly to approve the idea. Their efforts bore fruit on May 6, 1853, when lawmakers chartered the "Baltimore and Potomac Rail Road Company", granting it the authority to construct a railroad from Baltimore via Upper Marlboro in Prince George's County and Port Tobacco in neighboring Charles County to a point on the Potomac River between Liverpool Point and the St. Mary's River in St. Mary's County, southermost in the state. The charter also allowed the construction of branches of up to 20 miles (32 km) in length.