South Australia (SA) is a state in the southern central part of Australia. It covers some of the most arid parts of the country. It is the fourth-largest of Australia's states and territories by area, and fifth largest by population. It has a total of 1.77 million people and its population is the second most highly centralised in Australia, after Western Australia, with more than 77 percent of South Australians living in the capital, Adelaide, or its environs. Other population centres in the state are relatively small; Mount Gambier, the second largest centre, has a population of 28,684.