What can I legally do on a company’s discrimination on my evaluation?

I've been working on retail for almost 20 years now. I worked for a store in the past from the year 2004 until 2011. I left the company because I was working overnights and there was no position available day and I was getting ill for working overnights. I returned to the company six months later as a new hire, were they never took into consideration my past retail employment and my seven year past history with the store and hired me at minimum wage. I ended up leaving and got hired else were which I end up quitting due to shortage of hours. I got re hired at the store in north Ohio seven months later after I left again at minimum wage this time with 7 and a half years of the store’s customer service, supervisory, sales history. I've been working on this location for 2 years now. What frustrates me is that they hired American and Afro American natives with no store or very minimal experience at a hired rate than I am with over 20 years and 10 of those years are devoted to the store. At the point, I was hired the store manager and her team. At the time they hired an Afro American at $10.75 per hour fulltime with a fast food a fast food as the only retail background. I was hired as $8.10 per hour with 11 years of store background and 10 of retail. Not only that, I had to train this person because she had no idea of what was going on at the front end. The majority of the cashiers look up to me as supervisor because of my extensive knowledge on the front end functionality and operations. Every year I've been rated as valued associated and management find any excuse to degrade me. Every time the customer service manager is not around I am the one that steps out to help. Last week there was a situation were 3 managers were call down at the register and they had no clue of what was going on and they end up canceling the customer's transaction, which made the customer cry and she end up coming over to my register were I solve the situation.