Where did the ongoing ‘do a good deed and the mayor of the town congratulates you with the key to the city’ in movies & shows come from? Was that ever a real thing?

Question

I’m watching family guy & Peter found a missing kid and as a reward the mayor gave him the key to the city (or town hall?).
I’ve also seen this happen in a few other movies.

Was this ever a real thing? Is this an inside joke I’m not aware of?

In: 2567

Answer 1

I’ve been to a couple of events where the mayor of my hometown gave out keys to the city to the guest of honor and each time he would always joke “There’s nothing in the vault!”