Wilmington and Susquehanna Railroad

Philadelphia, Wilmington and Baltimore Railroad

PW&B flatcars sit outside the old Gray's Ferry Tavern in southwest Philadelphia, ca. 1870s
Locale	Pennsylvania, Delaware and Maryland
Dates of operation	1836–1902 (purchased 1880 by the Pennsylvania Railroad)
Predecessor	Baltimore and Port Deposite Rail Road Company, Delaware and Maryland Rail Road Company, Philadelphia and Delaware County Rail-Road Company, Wilmington and Susquehanna Rail Road Company
Successor	Philadelphia, Baltimore and Washington Railroad
Track gauge	4 ft 8 1⁄2 in (1,435 mm) standard gauge
Length	669 mi (1,077 km)
Headquarters	Philadelphia

The Philadelphia, Wilmington and Baltimore Railroad (PW&B) was an American railroad company that operated from 1836 until a merger in 1902. It built the first rail line south from Philadelphia.

Founded in 1831 as the Philadelphia and Delaware County Rail-Road Company, the PW&B had within six years changed its name and merged with three other state-chartered railroads to create a single line between Philadelphia and Baltimore. In 1881, the PW&B came under the control of the Pennsylvania Railroad (PRR).

An 1895 history of the PRR had this to say about the significance of the PW&B:

"An important constituent of a great North and South line of transportation, it challenges ocean competition and carries on its rails not only statesmen and tourists but a valuable interchange of products between different lines of latitude. As a military highway, it is of the greatest strategic importance to the national, industrial, and commercial capitals – Washington, Philadelphia and New York. It presents some of the very best transportation facilities to the commerce of the cities after which it is named and could not be obliterated from the railroad map of the United States without materially disturbing its harmony."

In 1902, the PW&B was merged into the PRR's Philadelphia, Baltimore and Washington Railroad.

The line is still in use as part of Amtrak's Northeast Corridor; and the Maryland state Department of Transportation's "MARC" commuter passenger system to the northeast of Baltimore. Freight is handled by Norfolk Southern and formerly Conrail.

On April 2, 1831, the General Assembly of Pennsylvania, seeking to improve transportation between Philadelphia and points south along the Atlantic coast and Eastern seaboard, chartered the Philadelphia and Delaware County Rail-Road Company. The legislature allotted $200,000 to build a rail line from America's largest city to the Delaware state line. In July 1835, surveyors began to look at possible routes, and in October, they reported that the best option, a 17-mile line, would cost $233,000 to build.