This is an amazing mountain sculpture in
progress, the first blast taking place
in 1948. It's not without controversy and it
has been operating without government
funds (and control) by choice.
Sculptor Korczak Ziolkowski was selected by members of
the Lakota tribe, who chose the Black Hills of South
Dakota for the location. Korczak moved to the Black Hills after
World War II and devoted the rest of his life to the project. He
died in 1982 and is buried somewhere near the base of the mountain;
his family/foundation carries on with the project.
In case you think you can walk up to the mountain and take
a look around, guess again. You must pay admission and take
the guided and timed bus trip there. The driver is full of information
and historical background so you probably won't be too irritated
by the fee. The sign is somewhat disingenuous as the
paid-for-bus-trips are allowed.
Museums, displays, and retail booths are all over
the place and you might as well check them out, because
you've paid for admission.
It's altogether stupendous and impressive, and will be even
more so when it's completed.
Here's the wiki info link
and here's a 35 second video driving away