Following Australia’s Federation in 1901, Brisbane entered the new century as the capital of Queensland, marked by civic celebrations and the laying of the foundation stone for St John’s Cathedral. The early decades were defined by labour unrest, including the 1912 Brisbane general strike, and political tensions during the First World War, such as the 1917 raid on the Queensland Government Printing Office and the Red Flag riots of 1918–19.

Civic expansion continued with the creation of the City of Brisbane in 1925, forming Australia’s largest municipal authority. Iconic infrastructure followed, including Brisbane City Hall in 1930 and the Story Bridge in 1940. During the Second World War, Brisbane became a major Allied headquarters in the South West Pacific, hosting General Douglas MacArthur at MacArthur Chambers and accommodating large numbers of American and Australian military personnel. Wartime pressures, from rationing to military construction, also led to civil unrest, exemplified by the 1942 Battle of Brisbane.

The post-war era brought large-scale immigration, suburban expansion, and increasing car ownership. The city’s vulnerability to natural disasters was underscored by severe floods, including the devastating 1974 flood, which prompted the construction of Wivenhoe Dam and major changes in water management. Under Premier Joh Bjelke-Petersen, Brisbane faced stringent restrictions on civil liberties, including bans on street marches and heavy police enforcement, which fueled civil rights protests, student activism, and a burgeoning artistic counter-culture. The city emerged as one of Australia’s early punk rock centres.

Civic and cultural renewal followed the end of the Bjelke-Petersen era. Reforms arising from the Fitzgerald Inquiry reshaped governance and policing, while the expansion of cultural institutions and urban redevelopment transformed Brisbane’s landscape. The city’s international profile was elevated by World Expo 88, which revitalized the South Brisbane riverfront. The site was redeveloped into the South Bank Parklands, opening in 1992 as a major cultural precinct and a symbol of Brisbane’s modern identity as a dynamic and cosmopolitan city.