My great,great,great grandfather came from Ireland in 1828 how do I find where h

Question:

My great,great,great grandfather came from Ireland in 1828 how do I find where he came from.?

I know his passenger # and he entered in Philadelphia.

Best Answer - Chosen by Asker: Lucky you, you have at least that info. My great someone came over in 1859 or so, anyway she married in 1861 and I have no idea from where in Ireland she emigrated. I heard Ballycotton, well that is a jumping off point, right there on the ocean. I doubt that is it, esp. given my source of info.
Please keep this question up for a little whiile to garner the most responses--I am also interested in the answer!