Joseph Benedict Chifley (September 22, 1885 - June 13, 1951), Australian politician and 16th Prime Minister of Australia, was one of Australia's most influential Prime Ministers. Among his government's accomplishments were the post-war immigration scheme under Arthur Calwell, the establishment of Australian citizenship in 1949, the Snowy Mountains scheme, the national airline Trans Australia Airlines, a social security scheme for the unemployed, and the founding of the Australian Security Intelligence Organization (ASIO). One of the few successful referendums to modify the Australian Constitution took place during his term.