imported post
http://www.silverwoodthemepark.com/rules.php
No weapons or firearms.
If you conceal and they catch you, you'll be asked to leave.
Personally, I don't think it's a good idea to mix "extreme sports", racing, roller coasters, etc with guns on our hips.
Edited to include OP's question. He asked if firearms were allowed at Silverwood Park in northern Idaho.
No big deal, it might be useful information to someone else too.