Just for public info, as of Feb '09 you are allowed to carry a conceal handgun in a National Park if the laws in that state allow for CC and that state has reciprocity with your state. The firearms laws of that state apply, not your state. You are prohibited from carrying in a federal building in the parks which would be the park headquarters, visitor centers, etc. I don't know if that include rest rooms. I'm also unsure about COE parks.
Concealed carry in states parks is governed by the laws of that state. In Texas, you can carry concealed in a state park and also LCRA parks. In Texas you are even allowed to have a concealed handgun in your vehicle without a permit because Texas has the "Castle Doctrine" and your vehicle is considered an extension of your home. That also applies to RVs. Some states even have provisions for possession in a vehicle if you are traveling, but the definition of traveling can be vague and you don't want to be a test case, so it would be prudent to check the laws of the state you are going to if you are going to be armed. I personally stay away from states that do not let me carry, or I lock it in a secure container.
2013 F250 XLT
I now have a Keystone Outback, but I try to help when I can.
Bitter Gun Owner