[1] McGee also vocally denounced the activities of the Fenian Brotherhood, a paramilitary secret society of exiled Irish Republicans who resembled his younger self politically, in Ireland, Canada, and the United States.

[3] In Wexford he attended a local hedge school, where the teacher, Michael Donnelly, fed his hunger for knowledge and where he learned of the long history of British rule and Irish opposition, including the more recent uprising of 1798.

In 1842 at age 17, McGee left Ireland with his sister due to a poor relationship with their stepmother, Margaret Dea, who had married his father in 1840 after the death of his mother 22 August 1833.

[4] In the United States, he achieved prominence in Irish-American circles and founded and edited the New York-based Nation and the Boston-based American Celt.

In common with several other Young Ireland émigrés, McGee espoused proslavery thought and defended the continuation of slavery in the United States.

In the 4 August 1849 edition of the Nation, McGee attacked supporters of the abolitionist Daniel O'Connell in the United States, writing that "Their task is to liberate their slaves, not to travel across the Atlantic for foreign objects of sympathy.

He accused the Americans of hostile and expansionist motives toward Canada and of desiring to spread its republican ideas over all of North America.

McGee worked energetically for continued Canadian devotion to the British Empire seeing in imperialism the protection Canada needed from all American ills.

In his editorials and pamphlets he attacked the influence of the Orange Order and defended the Irish Catholic right to representation in the assembly.

At Quebec, McGee introduced the resolution which called for a guarantee of the educational rights of religious minorities in the two Canadas.

[11] Moderating his radical Irish nationalist views, McGee denounced the Fenian Brotherhood in America that advocated a forcible takeover of Canada from Britain by the United States.

Following the Confederation of Canada, McGee was elected to the 1st Canadian Parliament in 1867 as a Liberal-Conservative representing the riding of Montreal West.

McGee was opening the door to Mrs. Trotter's Boarding House in Ottawa when he was shot in the head by someone waiting for him on the inside.

A final factor explaining the influence of the Fenians was the courting of the Irish Catholic vote by Canadian non-Catholic politicians.

[19] There is a monument to him in his native Carlingford, County Louth, unveiled during a visit in 1991 by then Prime Minister of Canada Brian Mulroney and Irish Taoiseach Charles Haughey.

His parents' grave in the grounds of Wexford's historic Selskar Abbey is marked by a plaque presented by the government of Canada.

[20] On 20–22 August 2012, the inaugural Thomas D'Arcy McGee Summer School was held in Carlingford, County Louth, Ireland to commemorate and celebrate his legacy.