McMinn was born in Newry, County Down, Ireland, a son of Joseph McMinn and his wife Martha McMinn, née Hamill, who with their large family emigrated to Adelaide on the Albatross, arriving in September 1850. Newspaper reports only mention Mrs McMinn and 8 children aboard Albatross. No details of his schooling are known, though it has been asserted that he was taught by one Mr McGeorge of Adelaide, however no teacher of that or similar name has yet come to light. It is likely the youngest children were home-educated, with the boys receiving tuition in drafting and surveying from a tutor.
Career
After completing school, he was articled to the architect James Macgeorge, and was appointed to the Architect-in-Chief's office, but in April 1864 left for employment as a chainman in Boyle Travers Finniss's 1864–65 expedition to Northern Australia surveying the area around Escape Cliffs and the Adelaide River. Following a breakdown of morale in the settlement, McMinn and six others purchased a 23-foot open boat which they dubbed the Forlorn Hope and sailed it to Champion Bay, near Geraldton, Western Australia. In late 1870 or early 1871 he was appointed as overseer of construction of the Overland Telegraph section from Port Augusta to Darwin, and on 3 May 1871 cancelled the contract tendered by Darwent & Dalwood, they having fallen behind schedule due to heavy rain. Critics of his action pointed out that with the onset of the dry season and better logistics this loss could easily have been made up. The work was put in the hands of engineer R. V. Patterson with instructions to finish the line by early 1872 no matter what the cost. McMinn was dismissed shortly after his return to Adelaide in July 1871, and William T. Dalwood was later awarded compensation of £11,000. McMinn began practising as an architect in 1867, briefly in partnership with Daniel Garlick, and later with some others, but usually independently. He designed many grand private residences, but also designed or assisted in the design of many of Adelaide's grand public buildings. Whilst in partnership with Edward John Woods, he designed the original Venetian Gothic building of the University of Adelaide, considered his greatest work.
Family
William McMinn married Mary Frances Muirhead at Glenelg on 14 March 1877; their family included:
Mary Muirhead McMinn married Charles Arthur Johns in 1913
Eileen Gordon McMinn married Rev. Harvey Langford Ebbs on 31 August 1904
Susanna Draper McMinn married Luke Michael Cullen, solicitor of Cullen & Wigmore in 1851. He was noted for shady and corrupt practices.
Mary McMinn arrived separately in July 1850 aboard Sultana, married William Brewer in 1857, lived in Kapunda
Jane McMinn married F. S. Carus Driffield on 22 January 1856
Three unmarried sisters: Sally or Sallie, Martha, and Elizabeth R. "Lizzie" McMinn ran a small school for girls from the family home, then in February 1884 founded Tormore House School, North Adelaide, which they ran for 13 years. They left for England on 15 December 1897, retiring to "Wolverton Gardens" in Ealing.
Gilbert Rotherdale McMinn, worked as a surveyor on the Overland Telegraph Line, in February 1871 discovering Simpsons Gap, which proved a better route for the line. He served in various senior public service positions in the Northern Territory. McMinn Street, Darwin is named for him.
Joseph McMinn married Charlotte Isabella "Chatty" Wells of Penola, was also a surveyor on the Overland Telegraph, later in charge of Willowie State forest, Wilmington, South Australia, where he died.
