For at least 40,000 years before European settlement in the late 18th century, the Australian mainland and Tasmania were inhabited by around 250 language groups of indigenous Australians. After sporadic visits by fishermen from the immediate north, and discovery by Dutch explorers in 1606, the eastern half of Australia was claimed by the British in 1770 and initially settled through penal transportation to the colony of New South Wales, founded on 26 January 1788. The population grew steadily in the following years; the continent was explored, and another five largely self-governing Crown Colonies were established during the 19th century.