[3] Gunn's father died when he was young, forcing him to work as a butcher's delivery boy to support his mother and siblings while studying at night classes.

Gunn's success with the Carters and Driver's Union led to his election as President of the United Trades and Labour Council of South Australia in 1911 and, as his star continued to rise, he was elected to Adelaide City Council in 1914, serving to 1916, when he became Federal President of the Federated Carters and Driver's Union.

[4] "Greatly respected for his tactful courtesy and self-control", Gunn entered the South Australian House of Assembly at the 1915 election as a Labor member for the Electoral district of Adelaide.

[5] A "Thousand Homes Scheme" was carried out to improve the quality and supply of housing for needy families, spending on education was increased, provided better medical facilities and new junior technical schools, higher wages for teachers, and more scholarships.

Gunn still raised the ire of conservatives through his plans to redraw the Assembly electorate boundaries, introduce a proportional representation electoral system, introduce adult franchise to the Legislative Council and establish a state government insurance commission, all of which were defeated by the conservative controlled Legislative Council.

Having gained a reputation as a competent administrator and Premier, Gunn surprised many when he suddenly resigned from the Premiership and parliament on 9 August 1926 to accept a Melbourne-based position with the Commonwealth Development and Migration Commission on a greatly improved salary.