This City is Weird

I was driving in downtown and I saw this sign:



I thought, "Phew, good thing I dropped my Nuclear Weapons off in the last town!"

Really, what is that sign supposed to mean? Aren't COUNTRIES supposed to be nuclear weapon free, or at least states-- a city declaring itself a "Nuclear Weapon Free Zone" is sorta like a waiter randomly declaring that his table is an "onion-free table." Anyway, it amused me so much that I almost got into an accident taking the picture.