Mark Hopkins Jr. was an American railroad executive. He was one of four principal investors that funded Theodore D. Judah's idea of building a railway over the Sierra Nevada from Sacramento, California to Promontory, Utah. They formed the Central Pacific Railroad along with Leland Stanford, Charles Crocker, and Collis Huntington in 1861.

Theodore Dehone Judah was an American civil engineer who was a central figure in the original promotion, establishment, and design of the First transcontinental railroad. He found investors for what became the Central Pacific Railroad (CPRR). As chief engineer, he performed much of the route survey work to determine the best alignment for the railroad over the Sierra Nevada, which was completed six years after his death.