1880 Town
South Dakota's 1880 Town has around 30 buildings from the 1880 to 1920 era. The buildings are furnished with thousands of historical accounts, relics, and photographs. There is also some Dances with Wolves movie props, a Casey Tibbs exhibit, and cool things to see and do especially for the kids.
There is a fee to get in for adults and kids but it is pretty cool and you can spend the day there. I highly recommend renting costumes and making a day of it. In the long run you can get some pretty cool pictures and it is more fun than just getting an old time photo at a store.
You need to check their website for prices, and hours. They are usually open from May until October depending on the season. During the summer it is extremely hot (no shade) so plan accordingly.