On this day....

July 7, 1930 - Construction began on Boulder Dam, later Hoover Dam, on the Colorado River. The Hoover Dam is regarded as one of the most extraordinary engineering feats of all time.

Hoover Dam Fast Facts:

Important Statistics
Hoover Dam is 726.4 feet high at its crest, and the towers on the parapet rise 40 feet above that. It's made from 3.25 million tons of concrete and weighs more than 6.5 million tons.

Working on the Dam
Construction started in April 1931 and was completed in March 1936. In total, 21,000 men labored on the dam, and the average total payroll was $500,000 per month.

The Earth Moved
Workmen removed more than 5.5 million tons of dirt and other materials and placed one million cubic yards of earth and rock fill. They also placed nearly 4.5 million cubic yards of concrete and drilled 410,000 linear feet of drainage holes.

Unusual Construction Fact

The dam was built using 215 blocks of various sizes that were connected by horizontal and vertical keys at the joints. Grout was then forced into the spaces to form a solid structure.

Building Boulder City
After constructions was completed, government and civilian employees needed housing to live nearby and operate the dam, and Boulder City was built. Seven miles of roads were constructed from Boulder City to the dam, along with 10 miles of railroad track. Another 22.7 miles of railroad track was laid from Boulder City to the Union Pacific line in Las Vegas.