Back in the 60s and probably later, Eglin was an open base.
Anyone who wanted to enter was waved right in. I guess if you looked really suspicious they might have stopped you.
On the other hand there were places on Eglin which were guarded by a guy with a rifle and they would not let you in unless you had darn good reason.
The Presidio of Monterey was an open post even in the 90s when I was there. It didn’t close until 9/11.