In February 1923, John Campbell Miles was travelling across the dry, hot Gulf Savannah not far from the deserted copper fields of Cloncurry, en route to the Northern Territory. Intrigued by what appeared to be mineralised outcrops by the banks of the Leichhardt River, Campbell Miles—armed only with a horse shoeing hammer—hacked off some of the dark coloured, unusually heavy stone and sent the samples off to the Government assayer in Cloncurry. They were found to contain as much as 78 per cent lead-silver. Campbell Miles's curiosity had paid off. The sometime-prospector had happened upon one of the richest known zinc-lead seams in the world.
Over the next two months, Miles pegged out the "Racecourse" lease in the area surrounding the outcrops, the larger of which he dubbed Mount Isa, laying claim to 42 acres of land that would become one of the most productive single mines in world history.
On 19 January 1924, Mount Isa Mines Ltd was established. It was Australia's most distant mine from sea port or coal field.
This isolation fostered a strong sense of loyalty and a deep camaraderie among the first settlers of Mount Isa. In sickness or celebration, triumph or tragedy, the people of Mount Isa stood together.
In 1927, Dr George Simpson accompanied a Qantas flight to transport an injured Mount Isa miner to the hospital in Cloncurry. The dramatic rescue illustrated the dangers and struggles faced by the pioneers of the outback who didn't have sufficient access to medical care, and clearly demonstrated the need for an urgent response medical service that could access these remote regions of the west. This event stands as the catalyst for the establishment of the Australian Inland Mission's Aerial Medical Service in 1928, now the iconic Royal Flying Doctor Service.