A former clerk in the Crown Solicitor's Office, Melbourne, John McEwen enlisted in the First AIF in the last year of World War I (1918). He later became active in the Victorian Farmers' Union and the Victorian Country Party. McEwen was elected to the House of Representatives in 1934 as a Victorian Country Party representative, but he soon shifted his allegiance to the federal Country Party, which was the junior partner in the coalition government led by Joseph Lyons.

McEwen was promoted to the ministry in 1937 as Minister for the Interior. He ceased to be a minister when the Country Party dropped out of the governing coalition when Robert Menzies first became leader of the United Australia Party. But he became Minister for External Affairs and, later, Minister for Air and Minister for Civil Aviation when the Country Party, by then led by Arthur Fadden, re-joined the government.

In Opposition for most of the 1940s, McEwen again became a minister in the Menzies government, which was formed in December 1949. He was Minister for Commerce and Agriculture (1949–56), Minister for Trade (1956–63) and Minister for Trade and Industry (1963–71). He remained in the ministry of the Liberal–Country party coalition until his retirement from politics in 1971.

McEwen was narrowly beaten for the Country Party leadership in 1939, losing to Arthur Fadden. But he was successful in 1958, when he succeeded Fadden as both Party leader and Deputy Prime Minister. McEwen became Prime Minister on 19 December 1967, replacing Harold Holt, who had disappeared while swimming off the Victorian coast. His period in office was short, ending on 10 January 1968 when the Liberal Party chose John Gorton to be its leader.

John McEwen died in 1980.

Initiated: Lauderdale Lodge No. 361 Victorian Constitution on 28 July 1926. Installed as Master of the Lodge on 10 October 1936.