You say that you've looked at the possibility of the line going to Germany...

My maternal grandmother's maiden surname was Slaughter. She often spoke of her family coming from Germany. She even spoke of how a couple of her relatives (cousins ?) had inherited a small castle in Germany, and that they had to sell it because they didn't have the money to pay for repairs and taxes due on it. I'm still searching for some evidence that said castle transactions actually existed.