Australia’s constitutional compromise required the new capital to be at least 100 miles from Sydney.
The rule appears in section 125 of the Constitution of Australia. It stated that the federal seat of government had to be in New South Wales, in territory owned or acquired by the Commonwealth, and “distant not less than one hundred miles from Sydney.” The same section also specified that Parliament would sit in Melbourne until the permanent seat was established.
This distance requirement was part of the federation-era bargain between Sydney and Melbourne. Sydney wanted the capital outside its immediate sphere, while Melbourne accepted a New South Wales location because the permanent capital would not be Sydney itself.
The constitutional wording uses imperial miles, not kilometres: 100 miles is about 161 kilometres. Canberra lies substantially farther from Sydney than that minimum. The figure is therefore a constitutional threshold, not an exact claim about Canberra’s road distance or a description of the city’s size.