The Transcontinental Railroad was a railroad built across the United States of America. Much of it was built by the Central Pacific Railroad, building east from Sacramento, California, and the Union Pacific Railroad building West from Omaha, Nebraska. The two railroads met at Promontory Summit, Utah. Much of it was built by people who came to the U.S. from China and Ireland. It cut the time to go across the United States from months to weeks and later days. At the time of its completion, it was one of the longest railroads in the world.