Australia became a nation on 1 January 1901 when the six colonies – New South Wales, Victoria, Queensland, South Australia and Western Australia and Tasmania – decided to federate, or unite. Through federation, the states transferred some of their law-making power to the federal Parliament.
The Australian Constitution, which outlines our form of government, was drafted at a series of conventions (meetings) attended by representatives of the colonies. These conventions were held between 1891 and 1898. The Constitution was then approved by a vote of the people in referendums held in each colony between June 1899 and July 1900. In deciding Australia’s system of government, the drafters of the Constitution were influenced by both the Westminster tradition of the British Parliament and by the federal model that existed in the United States. As a result, Australia’s system of government is often referred to as ‘Washminster’. For a detailed look at federation and the drafting of the Constitution, check this out.