(1868 - 1874).
The First Transcontinental Railroad is the popular name of the U.S. railroad line (known at the time as the Pacific Railroad) completed in 1869 between Council Bluffs, Iowa/Omaha, Nebraska (via Ogden, Utah and Sacramento, California) and Alameda, California. By linking with the existing railway network of the Eastern United States, the road thus connected the Atlantic and Pacific coasts by rail for the first time. Opened for through traffic on May 10, 1869, with the driving of the "Last Spike" at Promontory Summit, Utah, the road established a mechanized transcontinental transportation network that revolutionized the population and economy of the American West.
Authorized by the Pacific Railway Act of 1862 during the American Civil War and supported by U.S. government bonds and extensive land grants of government owned land, it was the culmination of a decades-long movement to build such a line and was one of the crowning achievements of the presidency of Abraham Lincoln, although completed four years after his death. The building of the railway required enormous amounts of money and feats of engineering and labor in the crossing of plains and high mountains by the Union Pacific Railroad and Central Pacific Railroad, which built the line westward and eastward respectively.
The building of the railroad was motivated in part to bind the eastern and western states of the United States together. The Central Pacific faced with the prodigious feat of building a road over the Sierra Nevada mountains started work in 1863. The Union Pacific company faced with the competition for workers, rails, ties, railroad engines and supplies by the needs of the American Civil War didn't start construction till July 1865. Completion of the railroad substantially accelerated the populating of the West while contributing to the decline of territory controlled by the Native Americans in these regions. In 1879, the Supreme Court of the United States formally established, in its decision regarding Union Pacific Railroad vs. United States (99 U.S. 402), the official "date of completion" of the Transcontinental Railroad as November 6, 1869.