Here is my husband and his sisters on a 1968 trip. We both remember the monument as being less well developed, just a small visitors' center and place to eat or buy souvenirs. Today it takes all day to see the museum displays and films, visit the sculptor's studio, and see the evening program and night lighting ceremony.
I had no idea about the original plans for the Mt. Rushmore monument until we saw the original model Gutzom Borglund made to guide his workers. The original plans included what you see here, but money concerns, the quality of rock lower on the mountain, and the sculptor's death halted work.
We walked a path under the monument that revealed all sorts of interesting alternate views. Maybe I'll give a shot at drawing or painting from the reference photos I took.