Illustrations
Frances and Anna around the time of their marriage
In addition to keeping scrapbooks, which his great granddaughter Mary Mooney Lesch has and is digitizing, O'Neill kept a lot souvenirs of events he had attended or at which he had served as judge, Below, from one of his multiple times as judge at a highland piper's contest
And from one of his two trips to the annual convention of Chief of Police
He belonged to Irish American societies and clubs: Below a medal from the "United Irish Societies" Meeting of 1902
He attended the 1897 Irish Fair, here advertised:

Held at "Battery D," an armory on the lakefront
And he kept a souvenir medal from the County Cork booth.
But O'Neill avoided the more radical Irish societies and kept his interest in Irish music quiet until he was "outed" by the media early in his first term as chief. England regarded the Clan Na Gael, for example, as a terrorist organization, and Clan Na Gael members had been involved in a notorious murder in 1889. In this cartoon from 1895, the magazine Puck depicts the Irish freedom fighter Jeremiah O'Donovan Rossa of the Clan Na Gael as an ape.
While the nativist, anti Irish and Anti Catholic journal America connected a love of Irish music to simian thuggishness.