"Keeper" wrote
Originally, no one, then it devolved to the Post Office. There shouldn't be any duplicates within a state, but I've found some using mapping programs. I think many are really neighborhoods, crossroads, railroad stations, or old names left on USGS maps rather than real towns. Many I've been through were just one farmhouse or a cemetery, or a flat spot where there used to be a grade crossing.
"Back in the day", immigrants weren't starting towns, they were moving to them. Generally they wanted to fit in and be Americans, so they picked "American-sounding" names for streets, businesses, and such.
KL