Volunteers pose for photos during the celebration for the 150th anniversary of the completion of the first U.S. transcontinental railroad, to which thousands of Chinese railroad workers have made great contribution, at the Golden Spike National Historical Park at Promontory Summit, an area of high ground roughly 100 km northwest of Salt Lake City, the United States, May 10, 2019. The first transcontinental railroad, also known as the Pacific Railroad, was a 3,000-km-plus continuous railroad line linking the eastern U.S. rail network with the Pacific coast. From 1864 to 1869, Chinese railroad workers, among the first Chinese immigrants to the United States, endured harsh working and living conditions to help build the mega project. (Xinhua/Li Ying)