Correspondence (1880-1936) consists of some 700 letters, 146 by Mahon and the remainder to him from 238 correspondents including Archbishop Carr (15), Alfred Deakin (4), J.S. Dowling (6), Lord Novar (12), Andrew Fisher (10), J.H. Fitzpatrick (8), Archbishop Mannix (4), J.H.P. Murray (5), Sir George Pearce (230 and James Smith (11). The correspondence generally results from Mahon's action in specific matters such as censorship of correspoondence with the Holy See (1915-1916), The Panama-Pacific Exposition, San Francisco (1915-1916) and affairs of the Northern Territory, Papua and Norfolk Is. The correspondence also covers Mahon's early years and imprisonment in Ireland. Half the collection consists of press cuttings relating to Mahon's political career and his interest in Catholic and Irish affairs.
Irish-born journalist who came to Australia in 1882, worked for Federation and was elected for Coolgardie in the first Federal Parliament. He held a number of portfolios between 1904 and 1916 under Watson, Fisher and Hughes. He was expelled from the House in 1920 for criticising British policy in Ireland.