He was a son of coal miner Archibald Hamilton de Largie and his wife Mary, née McLaren, both of whom died while he was very young.

[1] De Largie, a devout Roman Catholic, left school in 1869, at the age of 10 years old to work in the Lanarkshire mines, where he became involved in the labour movement.

[2] De Largie's union activities eventually led to his ban from working as a miner in Newcastle, forcing him to move to the Western Australian goldfields in 1896.

[2] De Largie's role with the AWA led to his prominence in labour politics and de Largie was elected president of the goldfields division of the joint Labor parliamentary committee in April 1899[2] and inaugural chair of the Western Australian Trades Union and Labor Congress.

[1] In 1907 he warned that Western Australia was in anti-Federation mood due to the lack of a transnational railway and in 1909 announced his support for compulsory military service, arguing that the Boers lost their independence because they were unable to defend themselves.