The document summarizes the construction of the Transcontinental Railroad in the United States in the 19th century. The Pacific Railway Act of 1862 called for the construction of the first transcontinental railroad to unite the country during the Civil War. The Central Pacific railroad company built eastward from California, while the Union Pacific built westward from Nebraska, using Irish immigrants, veterans, and thousands of Chinese laborers. The two lines met at Promontory Summit, Utah in 1869, dramatically reducing travel time across the country and ushering in population growth and development in the American West.