The first of two referendums on the proposed federal constitution was put to South Australian voters on 4 June 1898, however knowledge of the results of the referendum held in New South Wales on the same matter, which failed to meet a vote threshold for that state, resulted in a low voter turnout.
South Australian referendum, 1898 Wikipedia
While in the mid-19th century, South Australians were staunchly opposed to federation, due to the dominance of the colonies of Victoria and New South Wales in issues such as trade and tariffs, as well as a desire to keep unique elements of South Australia intact,. The mood shifted by the 1890s, with what was seen as the looming inevitability of federation a motivator to negotiating a good deal for the smaller states, with the argument by the Yes campaign that they may never have such favourable terms again. The No campaign however focused on the potential for increased costs for South Australians, as well as decreased land values.
Despite a low turnout, the referendum passed with a two-thirds majority.