In more than 100 years Killarney has grown into a thriving and prosperous rural community. Rooted deeply in agriculture, the first permanent settlers to the region were homesteaders, coming from all corners of the world, looking for adventure, freedom and affordable farmland. But before the settlement of these pioneers, this area was well known by fur traders, explorers and Natives who lived and trapped along the northern edge of the Turtle Mountains, which straddle the Canada-U.S. border to the south of Killarney.

Land surveyor and homesteader John Sydney O’Brien named Killarney Lake, because the landscape reminded the Irishman of home. "I think we should call this lake Killarney, after the beautiful hills of the homeland,” said O’Brien. He then dumped a pint of the Irish in the lake and baptized it Killarney.

The 1880’s were busy years, with the establishment of the R.M. of Turtle Mountain in 1882. The following year the first store was built in the community that was quickly forming near Killarney Lake. In 1885 the railway came through and by the following decade the population grew to 300 people. In 1903 Killarney was incorporated as a village, breaking away from the R.M. of Turtle Mountain.

Three years later, in 1906, it officially became a town. The community has struggled and succeeded through two world wars and the Great Depression. With the success of the entire rural and urban community in mind, the Town of Killarney and R.M. of Turtle Mountain have worked as partners to provide the best possible services and opportunities for growth to local residents. In recent years it became apparent that officially combining their resources could only make the community stronger.

On January 1, 2007 the two municipalities made the historic move to merge back together, like they were in the very beginning, to form the newly amalgamated Municipality of Killarney-Turtle Mountain.