(CNN)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 stands 5,725 feet above sea level.
More than two million tourists visit each year. In 2014, 2,144,808 people visited the monument.
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, 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.