Political map of Australia, New Zealand & the Southwest Pacific 01 July 1851 (Colony of Victoria): Following a decade of settler pressure, the Port Phillip District was separated from New South Wales as the new Colony of Victoria in 1851 (Separation of Victoria). At the same time, discoveries of gold north of Melbourne sparked what would soon become one of the largest gold rushes of the nineteenth century (Victorian gold rush). Within just three years Victoria would overtake New South Wales to become the most populous colony in Australasia—a position it would hold until 1892—and for a brief period Melbourne would be the second largest city in the British Empire after London.