The Big Four Entrepreneurs (AKA The Associates) were Leland Stanford, Collis Huntington, Mark Hopkins, and Charles Crocker. Between them, these four men took on the massive task of planning, funding, and constructing the very long railroad. Construction took over three years and cost an unknown final number of lives and money.
The main workforce were composed of Chinese emigrants who were considered just above slave labor. These emigrants laid the majority of all the rails and dug most of the tunnels that connected the two halves of the rail. The tunnels were dug to offset the most important obstacle: snowfall. Civil engineer Theodore Judah estimated that the average snowfall would be about thirteen feet across various areas of the rail, but a combination of tunnels and specially-fitted snowplow engines could keep the lines open with little trouble. The tunnels were dug with both manual labor and blasting: the former involved laborious drilling with three men operating hammers and a long chisel; the latter mostly involved black powder, although Tunnel #6 became the first use of the new formula Nitroglycerin, which became a major factor and saved time and money over the construction period. To combat the snow, about 37 miles of special Snow Sheds were also constructed, covering long sections of track and saving time in clearing after each snowfall.