The loop is easy to hold in your head: out to the Badlands, back to Rapid City, then into the Black Hills and back again. I would spend the hours like this, with the reasoning attached so you can move pieces around when the weather argues with you.
Day 1: Badlands National Park, Then Back to Rapid City
The park covers 244,000 acres of sharply eroded buttes, pinnacles, and spires, sitting inside the largest protected mixed grass prairie in America. On the ground, that means long sightlines, soft banded rock and a horizon that keeps rearranging itself as you drive. It is the opposite of a mountain park. Nothing towers over you, and the scale arrives slowly, which is why the first overlook can feel underwhelming and the fourth one does not.

Take the Overlooks Before the Light Hardens
Arrive early. The rock here is pale and soft, and it reads in low sun with shadow filling the gullies; by mid-morning the light comes straight down, the bands flatten out, and everything starts to look like the same photograph. Early also means you get the pullouts to yourself, and out here a pullout to yourself is the whole point.
Do not rush the first hour. Drive the park road, stop at more places than you think you need to, and get out of the car at each one. The Badlands are a place you understand with your feet and your ears, not through a windshield, which is why the order of this morning matters: overlooks first, a walk in the middle of it, and the roadside stop saved for the way out rather than spent at the start.
Walk Out Among the Spires
Somewhere in the middle of the morning, park and walk away from the road for a while. The ground crunches, the spires stand close together, and the prairie grass runs between them. You do not need a plan for this. Pick a line that looks walkable, follow it until the view opens up, and turn around when you have had enough.
Is it worth carrying water and a jacket on a walk that short? Yes, both. The wind shows up without warning, and shade is hard to find out there. If you would rather have the driving, the stops, and the commentary handled for you, a Badlands tour does the park with a guide and takes the navigation off your hands.
Wall Drug and the Drive Back
Wall Drug Store is the stop most people make on the way out, and it earns the pause whether or not you like roadside attractions. Stretch, eat something, buy the coffee, then point the car back toward Rapid City. You will be in town with the evening still ahead of you, which is the reason to front-load this day instead of spreading it.
Day 2: Mount Rushmore and the Black Hills
Day two is the human half of the trip: a mountain that people shaped into four faces. The drive into the Black Hills is greener and tighter than the prairie, and the memorial appears later than you expect, around a bend, above the town of Keystone.

Standing Under the Faces
The memorial is a 5,725-foot granite mountain, and the four faces on it are 60 feet tall: George Washington, Thomas Jefferson, Theodore Roosevelt, and Abraham Lincoln. Gutzon Borglum designed the sculpture, and his son Lincoln Borglum finished it, with 400 workers using dynamite, jackhammers, and chisels between 1927 and 1941. The grounds cover 1,278 acres, and close to three million people come through in a year.
That last number is the reason to arrive in the late afternoon and stay into the evening rather than treating this as a lunch stop. The faces do not change with the light so much as the mood around them does, and the crowd thins out as the evening comes on.
The Presidential Trail
Walk the Presidential Trail if the weather allows. It is the difference between looking at the sculpture and standing underneath it, and it takes you past the slope of fallen rock below the faces, where the scale finally makes sense.
Give the Lincoln Borglum Visitor Center a look on the way back. The exhibits on how the carving was engineered answer the question the faces raise, which is how anyone did this with the equipment of the 1930s. If you want the site interpreted rather than just viewed, a Mount Rushmore tour pairs the memorial with the surrounding Black Hills stops.
The Sculptor's Studio and the Evening Lighting
From May to September, the Sculptor's Studio opens and holds a scale model of the mountain, which is the closest you get to seeing the plan instead of the result. Stay on for the Evening Lighting Ceremony, which runs from mid-May to late September: a ranger talk at an outdoor amphitheater, then the slow exposure of light until the monument is fully lit. It is the one scheduled thing on this trip I would build the day around.
Crazy Horse Memorial sits on the same circuit, and the day works better with it slotted in ahead of the monument rather than after. Two carved mountains in one afternoon is a lot of stone. One of them at dusk is the version worth keeping.