John Alexander Mathieson was born on the 19 May 1863, in Harrington, Prince Edward Island to Ronald Mathieson and Anne Stewart. John worked for several years in a grocery store in Charlottetown and at a fish plant in Miminegash before attending Prince of Wales College in Charlottetown where he obtained a teachers certificate. He taught school in DeSable and in Manitoba before returning to PEI where he articled with a Charlottetown law firm. In 1894, Mathieson was admitted to the Bar, initially practicing law in Georgetown, and later in Charlottetown. On the 15 September 1896, John married Mary Alice, daughter of the Hon. David Laird.

John's political career began in 1903 when he was elected as the Conservative member of the legislature for Murray Harbor. By 1905, he was leader of the opposition. Elected in 1911, Mathieson became Premier and Attorney General, a post he retained until 1917. That year he was appointed as Chief Justice for PEI, a position he held for twenty-six years. John A. Mathieson died in January of 1947.