Creating the Massive Sculpture
To create the likeness of the four presidents, Borglum first constructed a model on a 1/12th scale. By placing a calibrated “pointer” device above the rock, he could then drop a plumb-line down the cliff face and multiply by 12 to precisely measure where the rock should be carved. Granite was blasted away using dynamite and the surface was precisely shaped using hammers and chisels.
The History of Mount Rushmore
The Black Hills, named for their dark granite surface, were formed by volcanic activity more than two billion years ago. This north-west region of the United States was inhabited by Native Americans for thousands of years, most recently by the Lakota Sioux, including Black Elk, a medicine man who often trekked the densely forested foothills on a spiritual journey, climbing to the highest point of the mountain range known today as Black Elk Peak.
In 1874, this part of South Dakota was overrun by gold miners and within a few years was renamed for Charles Rushmore, a businessman from New York who traveled west on hunting and fishing trips (Rushmore later donated $5K to the Mount Rushmore project).
The idea for a “larger than life” sized sculpture originated with Doane Robinson, a historian searching for ways to attract tourists to South Dakota. As the project evolved in the 1920’s, funding from Congress was secured and Robinson consulted with Gutzon Borglum, an American son of Danish immigrants who had worked on other historically themed sculptures.
Approximately 500,000 tons of rock was carved out of the Black Hills to form the 60 ft tall likenesses of the American presidents; Washington (America’s founding father), Jefferson (Expanded the boundaries of the US with the Louisiana Purchase and authored the Declaration of Independence), Roosevelt (A conservationist who worked to regulate American industry) and Lincoln (Fought the Civil War to keep the North and South united).
Preservation of Mount Rushmore is ongoing. Geologists estimate that Black Hills granite erodes at the pace of 1 inch every 10,000 years, so the faces of the iconic presidents should be visible for quite some time!