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. There is disagreement regarding the exact history of the breed prior to its arrival in the United States, and thus no official consensus on the origin of its name or association with Australia. For many years, Aussies have been valued by stockmen for their versatility and trainability. While they continue to work as stock dogs and compete in herding trials, they have earned recognition in other roles due to their trainability and eagerness to please and are highly regarded for their skills in obedience. 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.