collie, breed of large, agile working dog developed in Scotland during the 17th and 18th cent. It stands from 22 to 26 in. (55.9–66 cm) high at the shoulder and weighs from 50 to 75 lb (22.7–34 kg). There are two varieties of collie; it is thought that originally the rough-coated or long-haired type herded sheep in the torturous climate of the northern Scottish hills while the less weatherproof smooth-coated collie drove cattle to market. Both varieties may be sable and white, blue merle, tricolored (black, tan, and white), or white. Although no thoroughly documented explanation of the origin of the collie's name is ever likely to be set forth, the following is probably the most reasonable. A type of sheep once found in the Scottish Highlands had black markings, either on the face or legs, and was called the "Colley" sheep. The dog that was bred and trained to herd these sheep was known as the "Colley dog," and, later, as the "collie." Today it is one of the most popular farm dogs and pets in the United States. See dog.