More than 90 percent of the sculpting work was done not with chisels or jackhammers, but with sticks of dynamite. The blasts removed about 450,000 tons of rock from the mountain between 1927 and 1941.
The dynamite blasted away rock and roughed out the figures to within three to six inches of the final carving surface.
That last bit of rock was removed by drilling holes close together in a honeycomb pattern, weakening the rock so it could be precisely removed.
The work was exciting, but dangerous. Drillers hanging from bosun’s chairs drilled holes deep into the rock. Then the powdermen packed dynamite into the holes and set the charges. Before the blast, workers would have to be cleared from the face of the carving. Workers in the winch house on top of the mountain would hand-crank the winches to raise and lower the drillers.
Despite the dangers, the 400 workers were happy to have good-paying jobs during the Great Depression. Many of them were out-of-work gold miners, so the drilling and blasting was something they new. And throughout the 14 years of the Mount Rushmore carving, not a single man was killed on the mountain.