Perth was founded in 1829 largely because the British feared the French would establish a colony in Western Australia.
In 1827 Captain James Stirling (1791-1865) sailed to the Swan River in his ship HMS Success. Stirling believed the area would be ideal for a settlement. He persuaded the British government to found a colony there, independent of the colony in New South Wales.
Perth was named after the birthplace of Sir George Murray who was British Secretary of State for the Colonies when the city was founded in 1829. (However Murray was not actually born in the town of Perth. He was born in Perthshire).
However this colony was not to be manned by convicts. Instead the government would sell land cheaply to private citizens. (Ignoring the Indigenous Australians who lived there). www.localhistories.org/perthaustralia