[1] He was the son of Archibald McCallum (1829–1905) from Glasgow, Scotland, who came to New Zealand in 1855 after a year in Victoria, Australia.

McCallum married Winifred Grady from Wellington on 15 September 1892 at the Terrace Congregational Church (located on the corner of Lambton Quay and Bowen Street) in Wellington.

[5] Their honeymoon took them to the Hot Lakes district, Napier, Auckland,[4] Sydney, Melbourne, Hobart, and Adelaide.

[5] By age 21, he passed his exam as a barrister and became a clerk with W. Sinclair, the Crown Solicitor for Marlborough.

[7] McCallum was re-elected in 1914 and 1919, but was defeated in the 1922 election by Reform's William Girling.