Southern Pacific Company, transportation system chartered (1865) in California and later reincorporated in Kentucky (1885) and Delaware (1947). Small railroads—known collectively as the Southern Pacific—were built and merged after 1865 in S California to provide feeder lines to the Central Pacific RR and eventually to provide connections between San Francisco and New Orleans. The Southern Pacific RR survived the Panic of 1873 and inadequate financing, and in 1883, after the company had purchased several Texas railroads, Houston, Galveston, and New Orleans were reached.

In 1884 the Southern Pacific and Central Pacific railroads—which were conceived and constructed as parts of one system—were combined under the leadership of Leland Stanford and Collis P. Huntington as a unit of interdependent systems. Edward H. Harriman gained control (1901) of the Southern Pacific after Huntington's death and expanded the lines. The Southern Pacific Company added several smaller railroads in the 20th cent. In 1923, after the U.S. Supreme Court had directed (1922) the company to separate the control of the Southern Pacific and Central Pacific railroads, the Interstate Commerce Commission allowed the Southern Pacific to lease the Central Pacific's facilities. The Southern Pacific soon gained control of several bus lines in the Far West and in 1938 took over the trucking service previously provided by the Pacific Motor Transport Company.

At the end of World War II the company failed to resume operation of its steamship services from New York City and Baltimore to Galveston, thus abandoning a service that it had operated for over half a century. After a series of mergers and divestitures in the 1980s, the railroad emerged as the Southern Pacific Rail Corporation, a public corporation with a large business in containerized truck-to-train freight. The 1980s and 90s, however, saw the railroad consistently lose money on operations, and in 1996 it was merged into the Union Pacific.

See S. Daggett, Chapters on the History of the Southern Pacific (1922, repr. 1966); N. C. Wilson and F. J. Taylor, Southern Pacific (1952); G. L. Dunscomb, A Century of Southern Pacific Steam Locomotives, 1862–1962 (1963); R. J. Orsi, Sunset Limited: The Southern Pacific Railroad and the Development of the American West, 1850–1930 (2005).