Welcome (soon) to South Dakota!
Ellsworth is near Rapid City. I'm on the opposite side of the state in Sioux Falls.
I haven't visited Rapid City yet, so I can't tell you too much about your local area. South Dakota doesn't have state income taxes, though if you'll be living on base, I'm not sure that applies to you. You'll be about 30 miles from Mount Rushmore. There are a lot of touristy things near Rapid City.
Well, that's about the extent of my knowledge!
Here's hoping someone else can fill in some more of what I don't know.