On our family vacation we were passing through the Columbia River Gorge (I-84 east of Portland) and stopped at the Bonneville Dam to see the Fish Ladder. I've been there before--inside the visitor center they have viewing windows where you can watch underwater as fish migrate upstream--very interesting. To access the visitor center you have to drive through the dam security gate. The security guard asked our purpose for visiting and did I have any firearms. I replied that I did and they were unloaded and locked in the car trunk (since my Missouri CCW permit is not honored in Oregon). The guard told me I was not allowed to enter the gate with firearms or even just ammunition. I asked if I could check my weapons at the gate during the visit and they replied they did not have facilities for that. I knew that firearms are prohibited in many (all?) federal buildings, but I had assumed they would be permitted if left in the vehicle. Nope. As I was turning around I saw the guard writing down my license plate number, presumably in case I returned. I saw them looking inside the vehicle before me, so I'm guessing if I came back they might want to look in my trunk.
If we knew this in advance, we would have left the guns and ammo at our lodge during the visit to the dam, but we'd already checked out and were on our way to our next destination, so we just had to skip the fish ladder.
They also have a fish hatchery and we did not have to pass through security to go there, so it was still a good stop. They have a giant sturgeon on display there. There's a website about Herman the Sturgeon, so I guess that's him we saw.