Here's some background information about the Mount Rushmore National Memorial, composed of sculptures of the faces of former Presidents George Washington, Thomas Jefferson, Abraham Lincoln and Theodore Roosevelt.
The monument is located on Mount Rushmore in the Black Hills of South Dakota.
It is carved in Harney Peak granite and each head is about 60 feet tall.
It stands 5,725 feet above sea level.
More than two million tourists visit each year. In 2017, 2,437,800 people visited the monument.
Following 9/11, the Parks Service made various security enhancements, such as installing security fencing, lighting and gates, improved existing mechanical systems, and purchased all-terrain vehicles for use in patrols and at special events.
1923 - The idea is suggested by Jonah "Doane" Robinson, secretary of the South Dakota State Historical Society.
October 1, 1925 - Mount Rushmore is dedicated as a national monument.
October 4, 1927 - Work begins on the monument. The sculptor/designer is Gutzon Borglum. Four hundred workers sculpt the monument using dynamite and drills. Workers use much smaller models (about one-twelfth the size) to envision the final product.
July 4, 1930 - The section of George Washington is dedicated.
June 10, 1933 - Franklin D. Roosevelt issues Executive Order 6166, making Mount Rushmore part of the National Park Service.
August 30, 1936 - Thomas Jefferson's section is dedicated.
September 17, 1937 - Abraham Lincoln's section is dedicated.
July 2, 1939 - The Theodore Roosevelt section is dedicated.
March 6, 1941 - Gutzon Borglum dies. His son, Lincoln Borglum, completes work on Mount Rushmore.
October 31, 1941 - Drilling on the monument is complete. It only takes six and a half years of actual work on the monument, but the Great Depression slowed down its completion due to lack of federal funds.