transportation company chartered (1862) by Congress to build part of the nation's first transcontinental railroad line. Under terms of the Pacific Railroads Act, the Union Pacific was authorized to build a line westward from Omaha, Nebr., to the California-Nevada line, where it was to connect with the Central Pacific RR—which was to be built simultaneously from Sacramento, Calif. Each railroad company, after completion of an initial 40 mi (64 km) of track, was to be granted 6,400 acres (2,589 hectares) of public lands and a loan of from $16,000 to $48,000 for each mile of track laid. In 1864, Congress doubled the land grant, considerably eased the terms of government loans, and allowed the two railroad companies to borrow private capital. Also in 1864 and again in 1866 the Central Pacific was authorized to build eastward beyond the Nevada line.
In 1865 construction of the Union Pacific was begun from Omaha westward, and a long succession of harrowing construction problems, Indian troubles, and delays were encountered. Nevertheless, on May 10, 1869, the Union Pacific joined the Central Pacific, NW of Ogden, Utah, thus connecting the Missouri River and the Pacific Ocean by rail and completing the nation's first transcontinental railroad. The joining of the roads was marked in ceremony by the driving of a golden spike.
Construction of both roads involved tremendous profiteering, and in 1872 the scandal involving the Crédit Mobilier of America, an ephemeral holding company to which most of the Union Pacific's liquid assets had been transferred (1867), was unearthed. The fraud, combined with later mismanagement and overextensions, left the Union Pacific with heavy financial burdens, and in 1893 the company went into receivership. It was reincorporated (1897) as the Union Pacific RR Company in Utah, and under the management of Edward H. Harriman the railroad was expanded, vastly improved, and stabilized.
n 1901, Harriman added the Southern Pacific (see Southern Pacific Company) and the Central Pacific to his expanding railroad empire, and his spectacular attempt to control the Northern Pacific led to the formation of the Northern Securities Company, a huge rail monopoly that controlled transportation throughout the Northwest. Under pressure from President Theodore Roosevelt, the giant holding company was dissolved by the Supreme Court in 1904. Four years later the court ordered the Union Pacific RR Company to relinquish its control of the Southern Pacific, and in 1913 the separation was completed.
The Union Pacific also acquired large holdings in railroads in the East and later gained control over Western motor-coach lines. In 1936 the railroad initiated the development of Sun Valley, Idaho, into a popular winter resort. The Union Pacific acquired the Missouri Pacific and Western Pacific RRs in 1982 and M-K-T RR in 1988. In 1995 it agreed to purchase the Chicago and North Western RR, and it acquired the ailing Southern Pacific in 1996. By 1997 the much-expanded railroad was plagued by accidents, late arrivals, and congested rail lines; federal regulators intervened, allowing two competing railroads to share Union Pacific's tracks, to keep shipments moving (the track-sharing order was lifted in 1998). Today the railroad, with around 33,000 mi (53,000 km) of track in the West, Midwest, and Gulf Coast regions, is a subsidiary of the highly diversified Union Pacific Corporation; in 1999 the corporation split the railroad operation into three semiautonomous units (for the northern, southern, and western sections of the system).