The transcontinental route opened the country to expansion; mail, supplies and trade items could easily be shipped in a matter of days. Population and cities began to boom along the tracks. Railroads became a symbol of progress and prosperity as they began to branch out around the country.

The completion of the Transcontinental Railroad in 1869 symbolized the unification of the United States and the fulfillment of "Manifest Destiny." Historically, it represented the end of the grueling and dangerous wagon train era, reducing a cross-country journey from six months to just six days. For the American public, it was a triumph of industrial engineering over the "impenetrable" Sierra Nevada and Rocky Mountains. Symbolically, the "Golden Spike" driven at Promontory Summit represented a nation healing and binding itself together following the devastation of the Civil War. However, it also symbolized a dark turning point for Indigenous populations; the railroad facilitated the rapid colonization of the West, the near-extinction of the buffalo, and the forced relocation of tribes to reservations. Economically, it symbolized the birth of a truly national market, allowing goods and ideas to flow freely between the Atlantic and Pacific coasts, which laid the groundwork for the United States' rise as a global economic superpower in the 20th century.