[1] It was initially known as the National Labor Party like its federal counterpart, but was renamed at a conference in June 1917.
[2][3] The party initially continued in government under Vaughan, but was subsequently defeated in parliament in July 1917, and thereafter served as the junior partner in a coalition with the Liberal Union under Archibald Peake.
[5][6] Nonetheless, the two parties contested the 1918 state election in coalition after a protracted period of negotiations.
Five incumbent MPs contested the election under the Progressive Country Party banner: Peter Reidy (Victoria), Edward Alfred Anstey and William David Ponder (North Adelaide), Frederick Coneybeer (East Torrens) and Thomas Hyland Smeaton (Sturt).
William Humphrey Harvey, who had not been up for re-election, remained as the sole survivor of the party in the Legislative Council,[12][13] but he subsequently joined the Liberal Union in July 1921.