Gloria - Look at the census records that have their children listed. See if all were b. in OH or some in Ireland. That might give a clue to when they arrived here. However, ships lists before 1850 are hard to find. Go to a good library that has a book (I've forgotten the name of it) that gives names of immigrants to the U.S. You might find his name there (probably more than one but you may be able to narrow it down from place, dates, etc.) From that you may be able to request a search from the National Archives, but they went up on costs, etc. last year. You must know the date arrived, place of entry and name of ship, which you can get from the book if he is listed. I found where my gr-gr-grandfather came from in Germany that way and got a copy of the passenger list with his name on it.