Many workers contributed to the construction of railroads. On the East Coast, Native Americans, recently freed black people, and white laborers worked on the railroads. On the West Coast, many of the railroad workers were Chinese immigrants.

The construction of the First Transcontinental Railroad in the United States (completed in 1869) relied on a massive, diverse labor force that faced grueling and dangerous conditions. The Central Pacific Railroad, building from the West, relied heavily on Chinese immigrants, who made up about 80% to 90% of their workforce. These workers performed the most dangerous tasks, including blasting through the solid granite of the Sierra Nevada mountains with nitroglycerin. The Union Pacific Railroad, building from the East, primarily employed Irish immigrants, many of whom were veterans of the Civil War looking for work. Additionally, the workforce included Mormons in Utah, emancipated African Americans, and various other European immigrants. These workers lived in mobile "Hell on Wheels" towns that moved as the tracks progressed. It is important to note that the railroad's expansion also had a devastating impact on Native American tribes, whose lands were seized and whose way of life was permanently altered by the "Iron Horse," creating a complex legacy of industrial triumph and human tragedy.