Why was Australia divided up into states?

Answer 1

Australian states were originally separate colonies. Each had their own colonial administrations, their own defence forces and laws etc. The six colonies joined together to become federated as one nation on 1 January 1901, then instead of separate colonies they became states belonging to one nation (Australia) under a federal government.

Answer 2

No particular person or authority divided Australia up into states. The states developed from colonies, and the colonies developed as parts of the continent were settled. The first colony was New South Wales, but when the British settled in the south and the west, the colonies of South Australia and Swan River (later Western Australia) were established. Van Diemen's land (now Tasmania) was settled originally as part of New South Wales, but was given its own colonial administration. Similarly, Victoria and Queensland began as New South Wales, but boundaries were established to divide them separately once the need arose. The six colonies federated as the nation of the Commonwealth of Australia on 1 January 1901.