ELI5: 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?

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?