Chapman was born on 10 July 1864 in Bong Bong, New South Wales. He was the son of Monica (née Cain; also spelt Kean or Kein) and Richard Chapman, his father being a wheelwright and publican. His mother was born in Ireland. His given name was spelled "Austen" until 1897.[1]
Chapman attended the state school in Marulan until the age of 14, when he was apprenticed to a saddler working in Goulburn and Mudgee. By 1885 he was operating Chapman's Hotel in Bungendore, close to the eventual site of Canberra. Chapman moved to Sydney in 1887 and went into partnership with Edward William O'Sullivan in an auctioneering firm, of which he was managing partner. He was also the proprietor of the Emu Inn on Bathurst Street. His partnership with O'Sullivan was dissolved in 1889, and he subsequently established the Royal Hotel in Braidwood.[1]
Chapman had a significant role during the selection of Australia's national capital site, Canberra. A strong advocate for the rival site of Dalgety—legislated as the capital site by the Seat of Government Act 1904—he stated in August 1906 that, "I will defend Dalgety to the end. Any change from the selection already made can only be achieved over my political corpse."[3]
In early 1908, he conceded that Canberra was "the second best site, but Dalgety easily stands first."[4] As the process finally reached its conclusion, later in 1908, Chapman was suffering ill health. In his absence, although he had been paired for the ballots so as not to prejudice the outcome, at the ninth ballot Dalgety went down to Yass-Canberra by 39 votes to 33.[5][6]
However, once Canberra had been selected, Chapman strenuously advocated the development of the site on the Molonglo River near Queanbeyan, which like Dalgety was in his electorate.[7] The success of his efforts benefited many of his friends who owned land in the area, and also greatly boosted trade in Queanbeyan, the nearest town to the site. He was still MP for Eden-Monaro at the time of his death in Sydney on 12 January 1926 of cerebro-vascular disease, before he could sit in the first Parliament House in Canberra, which opened in May 1927. He was survived by his wife, two daughters and two sons, James Austin Chapman and John Austin Chapman who both became distinguished soldiers.[1][8] The Canberra suburb of Chapman was named after him.[9]