How was the transcontential railroad built?

The Transcontinental Railroad was built through a massive collaborative effort between two main companies: the Central Pacific Railroad and the Union Pacific Railroad, which began construction in the 1860s. The Central Pacific started in Sacramento, California, and moved eastward, primarily employing Chinese laborers, while the Union Pacific began in Omaha, Nebraska, heading west. The two lines met at Promontory Summit, Utah, on May 10, 1869, where the famous "Golden Spike" was driven to mark the completion of the railroad. The construction faced numerous challenges, including difficult terrain, harsh weather, and labor shortages, but ultimately revolutionized transportation and commerce across the United States.