Directly behind the heads is a pleasant little box canyon. Along one side is the unseen back of the memorial. Along the other side is the entrance to the incomplete Hall of Records. Carvers managed to create the entrance and a tunnel that extends 70 feet into the rock. However, in July 1939 Congress directed that all work be done only on the four faces. Borglum died in March 1941, and his son Lincoln Borglum wrapped up the drilling in October of that year. After Pearl Harbor attack on Dec. 7, 1941, World War II consumed American interest and resources. The Hall of Records was abandoned.
Fast forward to 1998. The Mount Rushmore National Memorial Society funded a project to carve a square horizontal box in the floor of the Hall, near the entrance. Inside this chamber, a teakwood box containing 16 porcelain enamel panels was placed. Etched into the panels was the story of America, including the Declaration of Independence, the Constitution, the Bill of Rights, biographies of Borglum and the presidents.
The cache was sealed with a 1,200-pound granite capstone. Carved into it are these words:
“... let us place there, carved high, as close to heaven as we can, the words of our leaders, their faces, to show posterity what manner of men they were. Then breathe a prayer that these records will endure until the wind and the rain alone shall wear them away."