He received his primary education at the local school run by his father then went to Trinity College Dublin, where he graduated at age 17.

When his brother died on 30 January 1877, O'Neill took over management of the paper, a position he retained until again retiring from newspaper work in March 1902.

[2] In addition to practicing law and his work in journalism, O'Neill was an active investor in real estate and industry, accumulating a fortune which at his death was estimated at $8,000,000.

[3] Eugene married Daniel's widow, Mrs Emily Martha "Emma" (Seely) O'Neill.

O'Neill died on 26 November 1926 at St Luke's Hospital in New York City after a three-month illness.