Hoover Dam: 726 Feet High, 1,244 Feet Long & 4.4M Cubic Yards Concrete

How did engineers build a 726-foot-high concrete dam across the Colorado River during the Great Depression? This is the incredible construction story of Hoover Dam, one of America's most iconic engineering achievements. Construction began in 1931 in the narrow Black Canyon, where engineers first had to control the Colorado River before the main dam could rise. Workers excavated massive diversion tunnels, stripped the canyon walls down to solid rock, and prepared the foundations for an enormous concrete structure. The finished dam rises 726.4 feet (221 m) above its foundation and stretches 1,244 feet (379 m) across the canyon. The dam and associated structures contain approximately 4.4 million cubic yards of concrete. One of the biggest challenges was simply placing that much concrete safely. Engineers developed an innovative system of interlocking concrete blocks and cooling methods because the enormous mass of concrete would otherwise take decades to cool naturally. The project ultimately used millions of cubic yards of concrete along with enormous quantities of steel, cement and excavation material. The construction was completed in the harsh environment of the Black Canyon in less than five years, with the final concrete placed in May 1935. The project was officially constructed during 1931–1936.