The two sides of the Transcontinental Railroad met at Promontory Summit, just northwest of Salt Lake City, Utah. On May 10, 1869, its final spike was driven, connecting the individual railroads built by the Central Pacific Railroad Company and the Union Pacific Railroad.
The Central Pacific built eastward, starting from Sacramento, California, and the Union Pacific built westward from the west side of the Missouri River. Although commissioned by President Lincoln in 1862, the Transcontinental Railroad project was delayed by the Civil War, and construction didn't start in earnest until 1865. Crews composed primarily of Chinese immigrants, Irish immigrants and Civil War veterans labored for four more years to build the 1,776-mile railroad.