Pennsylvania Railroad, former U.S. transportation company; inc. 1846 by the Pennsylvania legislature. It opened in 1854 as a single-track line between Philadelphia and Pittsburgh. Beginning in 1857, the company purchased many railroads, most notably the Allegheny Portage RR, that were owned and operated by the state of Pennsylvania. During the Civil War the Pennsylvania RR played an important role in the Union war effort. In the last decades of the 1800s, especially under the presidency of Thomas A. Scott (1874–80), the railroad rapidly extended its operations between the East Coast and the Mississippi River and between the Great Lakes and the Ohio and Potomac rivers. In 1910 a tunnel under the Hudson River allowed the railroad to reach its new terminal in New York City, known in the mid-1900s as the world's busiest rail station. The Pennsylvania RR introduced many innovations to railroading, including air conditioning, electrification, and the practice of loading truck-trailers on flat cars. In 1968, after a long legal battle that reached the U.S. Supreme Court, the Pennsylvania RR merged with the New York Central RR to form the Penn Central Company.
See J. C. Van Horne and E. E. Drelick, Traveling the Pennsylvania Railroad (2002).