People wanted to move west, especially after the California gold rush in 1849. After years of debate, in 1862 Congress passed the Pacific Railroad Act to build a transcontinental railroad. The Union Pacific Railroad would lay track westward from Omaha, Nebraska, and the Central Pacific Railroad would lay track eastward from Sacramento, California.

Many problems faced the builders of the transcontinental railroad. At that time, it was difficult to get supplies and workers because of the Civil War. The Central Pacific hired mostly Chinese and Irish immigrants to do the dangerous work of blasting the mountains with gunpowder. The Union Pacific hired mostly Irish and German immigrants at low wages. Many were killed or injured, especially the workers of the Central Pacific.

Near the completion of the railroad a race heated up between the Union Pacific and the Central Pacific. An all-time record was set when the Central Pacific finished 10 miles of track in one day. Finally, on May 10, 1869, at Promontory Point, Utah, the two railroads met and the job was completed.