The Australian Shepherd, often known simply as the 'Aussie', is a medium-sized breed of dog that was, despite its name, developed on ranches in the United States during the 19th century. However, the Border Collie was not used to create the Australian Shepherd. The Australian Shepherd most likely is the descendant of Carea Leonés, Pyrenean Shepherd and Old German herding dogs that were brought over by shepherds. For many years, Aussies have been valued by stockmen for their versatility and trainability. Like all working breeds, Aussies have considerable energy and drive. They often excel at dog sports such as dog agility and frisbee and are also highly successful as search and rescue dogs, disaster dogs, detection dogs, guide dogs, service dogs, and therapy dogs. They are considered the 17th-most popular dog breed in the United States. 1 Physical traits. They are considered the 17th-most popular dog breed in the United States. 1 Physical traits.