Companies in the late 1800s to early/mid 1900s would build towns and housing around the mines and pay workers in "credit" only redeemable at the company store for necessary goods, food, etc. Due to the high prices and single company monopoly over all aspects of life there, people would go into debt and be essentially locked in with fences like prisoners and forced to work off the debt.

Just West Virginia things

I'm gonna tell you in the form of a song!

Here is some background on what a company store is:

https://en.wikipedia.org/wiki/Company_store