I did some detective work to find out exactly how they came to that number. So I asked a friendly manager at Wendy's as we waited for our food.
"I have no idea," he replied. "It must be something to do with the census."
I was satisfied with that answer, so I asked him which of the 56 nationalities he represented.
"Me? I'm Heinz 57!"
"I don't get it..."
"Well, I'm like Heinz 57 steak sauce. There are 57 ingredients on Heinz 57, and I'm pretty sure I have 57 different types of blood in me. I'm part English, part Swedish, with a little bit of Dutch thrown in...and a bunch of other stuff."
I think they should change the sign to read: "Welcome to Rock Springs. Home of Heinz 57."