If they are in your bar, buy 'em a beer. (Or pick up the tab) It says tons to them. In Wisconsin, I reckon they are probably local folk serving. On the seaboards, they could be from anywhere. Just friggin' do it, you can swing it.
When I was a lad, a lady in Jacksonville, NC did my laundry and dry-cleaning for free in her laundry/dry-cleaning business. I have no idea of how many other young Marines she extended that same kindness to. It WAS her business, us. Korean lady... would not accept my money, no how.
I cannot begin to tell you how wonderful a gift she gave me, especially in those times of hating on the military.