Denieffe, Joseph (1833–1910), Fenian, was born in Kilkenny city, eldest son of an artisan (d. 1855); other details of his family are not known. He had a fringe involvement with one of the Young Ireland confederate clubs set up in the early summer of 1848. Emigrating to the USA (June 1850), he found employment as a tailor's cutter in a clothing firm on Broadway, New York. He enlisted in the Emmet Monument Association (EMA) in early June 1855. Some weeks later he felt obliged to resign from his job to protect the interests of a sympathetic employer whose firm was under threat from anti-immigrant ‘Know-Nothing’ groups. Deciding to return to Ireland to see his seriously ill father, he first called for military instructions to Michael Doheny (qv) of the EMA, who charged him ‘to do what you can for the organisation and for yourself’, on the understanding that insurrection was due to take place in September that year, following an armed Irish-American landing in Ireland. Bemused to find that the EMA had no links whatsoever in Ireland, he set out to embody likely Irish volunteers into the EMA after getting to Kilkenny city in late July. Despite the hazy nature of his commission he found few misgivings among the artisans and tradesmen he swore in, there and in Callan, most of whom retained their connection with secret conspiracy into the 1860s. Through John Haltigan, foreman printer on the Kilkenny Journal, he made acquaintance with Peter Langan, lumber merchant of Dublin city and leading nationalist militant. Having set up the elements of a working separatist movement and avoided police notice, he was let down by the overthrow of Irish-American plans in late August 1855. About to return to New York in September, he was inspired by the overwhelming confidence of James Stephens (qv), fresh from Paris, to stay and build up membership. From that point on it is clear that Denieffe was content to be subject to Stephens – indeed, he never had leadership ambition.
After two years of apparent political inactivity while employed as tailor's cutter in Carrickmacross, Co. Monaghan, and in Belfast (among comradely Orangemen), he was summoned by Stephens to Dublin on 23 December 1857. He was required to transmit Stephens's positive reply to the invitation of Doheny and John O'Mahony (qv) to regenerate revolutionary organisation in Ireland. He trusted Stephens more than most Irish-Americans did at this juncture, and was disillusioned to find in New York (January 1858) derisory organisational commitment and fund-raising ability. Getting back to Dublin on 17 March with a contribution towards revolutionary expenses and a message ceding authority to Stephens from the EMA, he was one of the first five members of the Irish Republican Brotherhood, founded by Stephens that night, when he was made a head centre. Sent again to New York in May 1858 to extract more money from nationalists, he stayed during this brief unproductive visit with an apologetic Doheny. Between June and August 1858 he journeyed with Stephens and Thomas Clarke Luby (qv) around the south of Ireland, recruiting to the IRB, and enraptured by the patriotic drive and culture of the ‘captain’. In late August he just evaded arrest near Gormanstown, Co. Meath. He passed May and June 1859 in Paris waiting for a course of military training, which did not take place. In the guise of an agent of a friendly society, the Brotherhood of St Patrick, he continued to initiate clerks and tradesmen, mainly in Dublin, into the IRB during 1859–60. He was later a principal in the formation of bogus athletic clubs, and even a quasi-legitimate engineering school, in Dublin, for recruitment purposes.
Acting under Stephens, he was one of the leading organisers of the funeral procession of Terence Bellew McManus (qv) on 10 November 1861. During 1861 he had established a gentlemen's tailoring firm in South Anne St. in Dublin, which served until 1863 as headquarters for Stephens; police were put off the scent by the affluence of his clientele. By 1864 he was one of many discontented with the autocracy of Stephens. Until late that year he dealt with Irish-American correspondence and financial contributions. After P. J. Meehan (editor of the Irish American) mislaid documents on his way to South Anne St. in October 1864, John O'Leary (qv) was made responsible for such administration. Some weeks after the Irish People was raided (September 1865), detectives arrested Denieffe at home. After three weeks’ detention he was fortunate to secure release on bail. At the special commission at Green St. in late November the evidence against him collapsed. He no longer felt Stephens had a mandate to command, but remained in touch with the IRB under Edward Duffy (qv). Called out on 5 March 1867 to support insurgent parties coming into Dublin from Tallaght, he was lucky not to be captured and took ship for Liverpool. After escape to New York he settled in Springfield, Ohio, until March 1887, when he moved to Chicago. He was active on the Devoy wing of Clan na Gael in both cities. He died suddenly of heart failure on 20 April 1910.
He married in 1859 and had several children.