Why is Western Australia in Australia?

Western Australia was one of the six colonies on the Australian continent that joined at Federation to make up the Commonwealth of Australia. Great Britain had already claimed the entire eastern seaboard, and wished to prevent the French from making a claim in the west of the continent. The fourth colony to be established, Western Australia was originally claimed by the British in 1829.

Australia is made up of 6 states and 2 territories, they are all close and/or connected together so it just makes it a part of Australia.