The Philadelphia, Wilmington and Baltimore Railroad (PW&B) was an American railroad that operated from 1836 to 1881. Formed as a result of the merger of four small lines dating from the earliest days of American railroading in the late 1820s and early 1830s, it was purchased by the Pennsylvania Railroad (PRR) in 1881, becoming part of their main line in 1902.
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 in three Middle Atlantic states to create a single line between Philadelphia and Baltimore. In 1881, the PW&B came under the control of the PRR, the largest railroad in the Northeast United States.
An 1895 historian of the PRR had this to say about the significance of the PW&B, which it had acquired and gained control of fourteen years before:
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.