Can you give us a birth date? First name? Any idea when he came over? Was he married? Did his wife come? He must have had kids if he is your gr-gr grandfather. Did any of his kids come to the USA? What brought him here? Siblings? Aunts, uncles, cousins? I am sure you have more information than you realize that could help us.
Please post all the information you know about him and if any of his children or wife came over. The more we have to work with the better chances we have to help you.