Fort Laramie National Historic Site: Originally a private fur trading post on the frontier. Eventually a US Army post.
Fossil Butte National Monument: A small site with fossils in the visitor center for easy viewing.
Grand Teton National Park: The Teton Mountains are the star of the show. However, there are quite a few other things to see.
Yellowstone National Park: The first National Park in the world, established in 1872. It’s impressive and should be on bucket lists everywhere.