There were a lot of O'Neill's in Franklin County New York after 1850. One of my cousins long ago (m) an O'neill there. Those census can be found at the New York Genweb site and at Rootsweb. Look in towns of Chateaugay, Burke, Belmont, Malone. Also a lot of Dwyers and Leary's there. Prob. from O'Dwyer and O'Leary as I did see some spelled w/the O'