Cantwell, James (1818–75), nationalist, was born in Co. Tipperary and had at least three brothers and two sisters; nothing else is known of his family background. By the early 1840s he was employed as a mercantile assistant in the firm of Kinahan, Sons, & Smyth at Carlisle Buildings, 26 D'Olier St., Dublin. Originally a supporter of the repeal movement, he sided with the seceding Young Ireland party in 1846 and subsequently took an active part in promoting the clubs of the Irish Confederation (established January 1847), particularly in Dublin. After the suspension of habeas corpus (25 July 1848), he fled to Thurles, Co. Tipperary, with P. J. Smyth (qv). On 28 July, at a revolutionary council meeting at Ballingarry, Co. Tipperary, which he attended, a decision was made to resist government coercion and, along with James Stephens (qv), he drilled men at Mullinahone. After an abortive attempt at resistance, Cantwell fled to America with John Blake Dillon (qv), settling in Brooklyn, New York. By the mid 1850s he had settled in Philadelphia, where he became a successful merchant. During 1859 he helped to establish the Fenian Brotherhood in Philadelphia. The following summer he was sent to Paris by John O'Mahony (qv) to meet James Stephens, and was thereafter delegated to perform an inspection tour of the IRB. After Cantwell reported to O'Mahony unfavourably on the state of the IRB, however, Stephens refused to work with him.
Deciding to live in Dublin, Cantwell married and by 1863 had taken over the management of the Star and Garter Hotel, 16 D'Olier St., which subsequently became one of the most successful hotels in the city. On the death of William Smith O'Brien (qv) in 1864, Cantwell, together with P. J. Smyth (qv), took the lead in planning the erection of a monument in Dublin in his memory. This was ultimately erected at Carlisle (later O'Connell) Bridge in 1870; it was removed to O'Connell St. many years later. During the mid 1860s, after the arrest of many IRB activists in Dublin, Cantwell aided the escape of several republicans to America or else provided for their families. As popular in liberal as in nationalist circles, he sympathised with, but did not take an active part in, the Amnesty Association (established November 1868), for fear of offending many of his political associates. A good friend of Isaac Butt (qv) and Patrick Egan (qv), during the early 1870s he was a member of the general committee of the Home Government Association shortly after its establishment (19 May 1870) and sat on the council of the Home Rule League (established November 1873), but continued to refrain from engaging directly in political activity. He died suddenly on 13 November 1875 at his residence in the Star and Garter Hotel.