After the gold rush wound down in the 1860s, the majority of the work force found jobs in the railroad industry. Chinese labor was integral to the construction of the First Transcontinental Railroad, which linked the railway network of the Eastern United States with California on the Pacific coast. Construction began in 1863 at the terminal points of Omaha, Nebraska and Sacramento, California, and the two sections were merged and ceremonially completed on May 10, 1869, at the famous "golden spike" event at Promontory Summit, Utah. It created a nationwide mechanized transportation network that revolutionized the population and economy of the American West. This network caused the wagon trains of previous decades to become obsolete, exchanging it for a modern transportation system. The building of the railway required enormous labor in the crossing of plains and high mountains by the Union Pacific Railroad and Central Pacific Railroad, the two privately chartered federally backed enterprises that built the line westward and eastward respectively.