Glengallan Shire, an area of about 1980 sq km, extended eastwards from Warwick into the dividing range. Its main town was Killarney, a few kilometres from the New South Wales border, but its shire chambers were in Warwick.
The shire was proclaimed as a local government division in 1879 and named after the Glengallan pastoral run, made famous by John Deuchar, a merino breeder. Deuchar built the equally famous Glengallan homestead in 1867, a two-storey, verandahed mansion with unsustainable upkeep costs. Situated five kilometres south-east of Allora and left unoccupied for decades, it was restored in 2002 as a heritage centre (2002).
Glengallan Shire had numerous fertile valleys and well wooded hills, with the headwaters of the Condamine River flowing through Killarney. In addition to the extensive timber and numerous sawmills, there were wheat and other crops, grazing and dairying. A railway (1885) ran in an arc from Warwick through Swan Creek and Yangan and then south to Emu Vale, Tannymorel and Killarney. There was a sandstone quarry at Yangan and coal mining near Tannymorel. In 1949 the shire was described in The Australian Blue Book:
In 1994 Glengallan shire was united with Allora and Rosenthal Shires, and Warwick City, to form Warwick Shire. Its census populations were:
Killarney, Tannymorel and Yangan entries