There’s an old political joke -- we first heard it during the Carter administration, but it’s been applied to every president since.
Q. Why won’t they add President ______ to Mount Rushmore?
A. There’s not enough rock for two more faces.
But there is a bit of truth to that. In fact, when sculptor Gutzon Borglum began his carving in 1927, he intended to put Jefferson to the left of Washington. In fact, crews spent time roughing in the third president’s visage to Washington’s left. But the rock surface proved unstable, and Borglum ended up blasting it off and starting again to Washington’s right.
A handful of photos exist showing the ghostly image of Jefferson.
Regarding the idea of adding future presidents to Mount Rushmore: don’t hold your breath. It doesn’t matter how much rock is carvable. The National Park Service is adamant that Mount Rushmore is a work of art by Gutzon Borglum -- and it’s a completed work. Nobody has the right to alter Borglum's artistic vision. It would be akin to painting the image of Sophia Loren onto the Mona Lisa.