John Augustine MacDonald was born in 1913 was the son of John Alexander MacDonald and Marie Josephine MacDonald of Cardigan. He appears to have shared his father's interests in business and politics. As well as serving as President of J. A. MacDonald & Co. Ltd. and Director of Associated Shippers, Inc., he was President of the Kings County Board of Trade, a Director of the King's County Memorial Hospital, and belonged to numerous social, cultural, political, military, and recreational clubs and associations.

In a by-election in 1945, John Augustine was elected to the PEI legislature while still hospitalized after being wounded in Normandy in July of 1944. He was defeated in 1947 and re-elected in 1951 when he served as Financial Critic and Party Whip. After two defeats in federal elections, he was elected to the House of Commons in 1957, and re-elected in 1958, where he served until his death in 1961.