In our research so far, Restaurant-ing through history, has been the best source. This is a page that gives the trends of foods and restaurants throughout the decades, helping us with our timeline of etiquette. In the past, it seems America had been very serious on their snacking of oysters. One sign said “DON’T STOP ME. I’m bound..TO GET MY OYSTERS. ” as a man with a trench coat stalks off.
This page is very informative, and goes into great detail people’s reactions to new restaurant styles at the time, although it does not mention etiquette as much.