Lassie was a rough collie. This is a dog that was developed in Great Britain, specifically Scotland, as early as the 16th century to herd sheep.
The rough collie is famous for its profuse double coat, with its abundant mane, frill between the front legs and bushy tail. The dog also has a long body, a long muzzle, and an intelligent and eager expression. The most-popular coloration is tan and white, but rouch collies are also are black-colored. Another thing that people might not know about Lassie is that she was always played by a male dog, whose coat is a bit more luxurious.