He attended Melbourne Church of England Grammar School (1878-1879), where he gained a reputation as an athlete.
He was admitted to Trinity Hall, Cambridge in 1882, where he began boxing – he later became the runner-up in the amateur light-weight boxing championship in England. A supporter of Sir George Reid, he was elected to the House of Representatives for Riverina in New South Wales in 1903 by only five votes, representing the Free Trade Party. On petition by the former member, John Chanter, however, the result was declared void on the grounds of electoral irregularities.
Blackwood, who lost the subsequent by-election, was cleared of all charges but never stood for parliament again.
Blackwood continued to be active in rural affairs, becoming vice-president of the Pastoralists" Union of Southern Riverina in 1906. He was president of the Conargo Shire in 1907, and represented many companies.
He became chairman of Dalgety & Company and Australian Farms Limited, and president of the Victorian Employers" Association and the Registered Clubs" Association of Victoria from 1916-1930. He also became vice-president of the Royal Agricultural Society from 1920-1938.
Blackwood married Constance Ferrier Mailton on 23 July 1895 at Street Paul"s Cathedral, Melbourne.
He had no children.
He was briefly a member of the Australian House of Representatives for the Division of Riverina. An active community member around Deniliquin, Blackwood was a member of the Pastoralists" Association of Victoria and Southern Riverina.