There are several sites in the Rapid City  area that are fun for kids and adults both. Dinosaur Park (940 Skyline Dr., 605/343-8687, year-round daily dawn–dusk, free) is likely one of the odder WPA projects. Built in 1936, the park is on the National Register of Historic Places.
For decades, these concrete sculptures—including a T. rex, brontosaurus, stegosaurus, and triceratops—have been watching the prairie horizon and welcoming visitors every day, year-round. The dinosaurs were originally gray, but now are painted green and white. They aren’t biologically accurate, but they are designed for good climbing. Have a seat on a dinosaur tail and enjoy the view.
The park’s visitors center (970 Skyline Dr., 605/343-8687, June–Aug. daily 8:30 a.m.–8 p.m., May and Sept.–Oct. daily 9 a.m.–5 p.m., closed in winter) carries a nice collection of dinosaur books and gifts, rocks, and fossils and also has a snack bar with sandwiches and ice cream.