We're in northern Colorado. My dd10 did the Exxon Mobil astronomy camp at the University of WY in Laramie a few weeks back and really enjoyed it. It's for kids entering 6th-8th grade and I'm sure that they'll run it again next summer if that might be a possibility for your kiddo.
Beyond that, I haven't spent much time heading up north into WY. I guess that, depending on where in WY you are, there might be some options in Fort Collins (northern CO) or western Nebraska or Kansas. The University of NE has an "all girls/all math" camp during the summer for instance:
http://www.math.unl.edu/programs/agam/ (I don't know your dc's age or gender!)
