In 1931 a construction contract was let to Six Companies, Inc., a consortium of six major western firms. Together with the government, they built almost 30 miles of railroad connecting Boulder City with all the facilities needed to build Hoover Dam (eg., cement mixing plants, quarry pit, gravel sorting plant).
The Hoover Dam construction railroad system had three segments. The first, from Las Vegas to the Boulder City site, was built and operated by the Union Pacific Railroad.
The second segment was built by the U.S. Government. It ran from Boulder City down Hemenway Wash to Himix, the concrete mixing plant on the rim of the Black Canyon overlooking the dam. It provided concrete for the dam and the buildings on its crest. The airline distance from Boulder City to Himix was 6.7 miles. A drop in 1,100 feet in elevation however, necessitated ten miles of winding tracks to keep the grades from being too steep.
Six Companies, Inc. built and operated the third segment of the system. The tracks branched off the U.S. Government Construction Railroad at Lawler, about a mile up Hemenway Wash from the Visitor Center. It crossed Hemenway Wash and followed the base of the River Mountains and then looped eastward to the gravel plant on the flat overlooking the Colorado River. One branch went upstream 7.3 miles from the gravel plant to the gravel beds on the Arizona side.
Isolation demanded the tons of concrete needed for the dam to be manufactured locally. An electric dragline with a five cubic yard capacity loaded gravel into railroad cars. Concrete was made by mixing sand and crushed rock, called aggregate, with portland cement and water. Over four million cubic yards of aggregate were taken from the Arizona side of the river.
The other branch followed the river downstream into Black Canyon, to Lomix, a concrete mixing plant situated at the base of Black Canyon. Lomix provided the concrete for the diversion-tunnel linings, the powerhouse foundation, and two-thirds of the dam. To prevent the concrete from drying during transportation the mixing plant was put as close to the river as possible.
Locomotives hauled tons of gravel to a screening plant on the other side of the river 24-hours a day. A round trip took slightly over two hours. Depending on lake water levels, the foundation may be visible on the Boulder Islands.
The Six Companies, Inc. Railroad was, of course, abandoned after the completion of Hoover Dam in 1935. The U.S. Government Construction Railroad section was sporadically used until 1961, when the last generator was hauled over its rails and installed at the power plant.
The tracks were dismantled in 1962 and sold as scrap. The tunnels and trail were nominated in 1984 to the National Register of Historic Places.
Today you can walk or bicycle along the elevated railroad bed used to haul supplies and materials for the construction of Hoover Dam. Enjoy the spectacular views of Lake Mead and the surrounding desert landscape.