I am trying to find out how my Sullivan family came to be here in the United States. Names I am searching for are Sullivan, and Clancy as that is all I know as my grandmother has passed and my great grandparents had passed before my aunt, my dad or uncle ,met them

I am trying to find out how my Sullivan family came to be here in the United States. Names I am searching for are Sullivan, and Clancy as that is all I know as my grandmother has passed and my great grandparents had passed before my aunt, my dad or uncle ,met them