A transcontinental railroad is a contiguous network of railroad trackage that crosses a continental land mass with terminals at different oceans or continental borders. Such networks can be via the tracks of either a single railroad, or over those owned or controlled by multiple railway companies along a continuous route. Although Europe is crisscrossed by railways, the railroads within Europe are usually not considered transcontinental, with the possible exception of the historic Orient Express.
Transcontinental railroads helped open up unpopulated interior regions of continents to exploration and settlement that would not otherwise have been feasible. In many cases they also formed the backbones of cross-country passenger and freight transportation networks.
A transcontinental railroad in the United States is any continuous rail line connecting a location on the U.S. Pacific coast with one or more of the railroads of the nation's eastern trunk line rail systems operating between the Missouri or Mississippi Rivers and the U.S. Atlantic coast. The first concrete plan for a transcontinental railroad in the United States was presented to Congress by Asa Whitney in 1845.
A series of transcontinental railroads built over the last third of the 19th century created a nationwide transportation network that united the country by rail. The first of these, the 3,103-kilometre (1,928 mi) "Pacific Railroad", was built by the Central Pacific Railroad and Union Pacific Railroad to link the San Francisco Bay at Alameda, California with the nation's existing eastern railroad network at Council Bluffs, Iowa/Omaha, Nebraska thereby creating the world's first transcontinental railroad when it opened in 1869. Its construction was made possible by the US Government under Pacific Railroad Acts of 1862, 1864 and 1867.