Which state was the last to adopt Australia Day as a public holiday?

South Australia was the last state to adopt Australia Day as a public holiday.

The date 26 January originally marked the raising of the British flag at Sydney Cove in 1788. New South Wales observed it as Anniversary Day, and by the 1888 centenary the other colonies had generally joined in—except South Australia. South Australia had been established as a free settlement rather than a convict colony, so it was less inclined to commemorate the penal-colony origins associated with the date.

In 1910, South Australia adopted 26 January as Foundation Day, replacing Accession Day. The national name “Australia Day” was promoted more widely during the First World War, initially on dates in July for fundraising. By 1935, all states were using the name Australia Day, although New South Wales still used Anniversary Day in some contexts.

The wording can cause confusion because national uniformity came later. The Commonwealth and states agreed in 1946 to unify celebrations around 26 January, while the holiday was often observed on the nearest Monday. Australia Day became a consistently observed national public holiday in 1994.