They damn near were. You lived in a rent controlled (by the company) home in a town where the company set all the rules. There was a company store that extended credit to employees pretty freely. If, however, you had a credit balance you couldn't quit until paid it off in full and your pay was docked automatically for the minimum payment on that balance.
So, yes, up through the 70's mining towns often were plantations where the company owned everything and the employee just got a varnish of freedom over the truth of being essentially "owned" by the company.