My family did a bit larger of a loop (no offense intended) that included South Dakota largely on the recommendation of this thread.
The family did Texas to Michigan, back to Chicago, to Wisconsin, Minnesota and into South Dakota.
There, we hit Badlands National Park, Spearfish Canyon, Deadwood, Keystone, Mount Rushmore, Crazy Horse Monument, Custer State Park, Wind Cave National Park, and then headed south into Wyoming.
On the way back to Texas, we hit Rocky Mountain National Park, Denver, Pikes Peak area, Capulin Volcano, Alibates National Monument near Amarillo and back home.
I think we beat the 3200 miles.
South Dakota is underrated in terms of how cool it is. I highly recommend it to anyone. I regret not making it to North Dakota or out west, but there is always next year. As you can tell, we aren't afraid of putting miles on the truck.