A lot were busy manufacturing, mining, or farming towns.

The mines run out or become unprofitable.

The manufacturing has largely moved to out of the states, or been automated.

And big farms and grocery stores have squeezed independent farmers out of everywhere but the farmers markets near rich cities.

The stereotype is always a coal mining town. There used to be a mine employing many people, but now it’s automated or the mine played out

The town I grew up in was a bustling town with one dominant employer. When that employer moved out it left a big gap and an entire generation of younger people moved away

The town my father grew up in was never bustling. However it was a significant center of a rural area with many family farms. By the time I was growing up, those farms were no longer economical, so people moved away and there’s no need for a population center

A small town I used to visit all the time was once a bustling tourist town, but no one goes there anymore. It’s really just regional now, instead of the busy season drawing people from anywhere between Montreal and NYC. It’s probably cheap flying as much as anything else: who wants to vacation on a cold beach when you can hop a flight down south for the same cost