A lot of those jobs were outsourced/offshored to China, India, and others. Once you get out of the prosperous major cities, many rural areas are really undeveloped and poor. Usually, there was some sort of plant or mill that was the local financial/employment hub, and long since gone.
No truer words. I grew up in a town of 3000 people. It was however the industrial center of the entire county. Five medium and a pair of smaller size manufacturers. But, in the span of less than a decade all were gone along with more than 1000 decent to good paying jobs .
Today when the borough council meets at the top of the agenda is to vote on which abandoned house they will tear down next.
There was 141 graduates in my boomer generation high school class. At last weeks commencement 61. Over in the next county part of my Ground route was a 300 square mile school district. At one time they had 8 elementary schools spread out over that 300 square mile district.
Today? They have 1. They simply took a wing off the junior high and made that the elementary school.
Will areas such as this recover? Now living costs here are naturally pretty low. But it will either take some type of global geopolitical event or the pressures of living in an under stress metropolitan area become such that it's just not worth remaining there.