U.S. railroad company founded in 1861 by a group of California merchants including Mark Hopkins and Leland Stanford .
It was built with land grants and subsidies from the Pacific Railway Act (1862); thousands of Chinese labourers were hired to build it. Its tracks joined with those of the Union Pacific on May 10, 1869, in Promontory, Utah, forming North America's first transcontinental railroad. From 1884 it was leased to the Southern Pacific Co., with which it merged in 1959.