filters and other equipment ???

[mjs1973]

I'm with Michael. A good circular polarizer is all you really need.

[Ronnoco]

I ended up in South Dakota and the badlands as a result of my father taking a wrong turn.
It was great for photography though. I was surprised to run into wild donkeys, and elk and the prairie dogs were cute to shoot as well. As to Mount Rushmore, you have to hit it in the morning, rather than later when shadows can become a challenge to deal with. Telephoto is definitely necessary. I used a 400mm for the elk on the other side of a river.

A polarizer is definitely useful to cut down on light, improve the sky, and reduce contrast.
A graduated neutral density filter (square kind) would be good for sunsets. A UV filter protects your lens, particularly when you step into a trench at dusk, while watching the sky instead of where you are going.

Have fun!

Ronnoco