While a highly adored and popular breed in the United States, most Americans do not know where Cairn Terriers come from. The first clue is in their name. A "cairn" is a mound of rocks or stones, usually stacked in a cone shape, that were used as landmarks or monuments in the Scottish Highlands, from which the Cairn Terrier originates. Cairn Terriers were initially bred to hunt and flush prey, vermin, or game that would hide in burrows beneath these cairns.

The Cairn Terrier's Scottish Highland origin has everything to do with the appearance, temperament, and abilities of the dog. The Cairn Terrier was developed for a very specific purpose. Their coat, for instance, has a thick undercoat for warmth and a relatively water-proof topcoat. This balance helps the terrier to survive through the varying and often harsh temperature and weather patterns found in the Scottish Highlands.

The Cairn's size is another factor intentionally bred into the dog. Farmers in the Scottish Highlands needed a dog tiny enough to follow vermin and other pests into burrows, aggressive enough to stand up to its prey, and stubborn enough to finish the job regardless of the fight the game animal might put up. Cairn Terriers excel in all these areas because of the careful and selective breeding that went into the development of the breed.

The Cairn breed achieved much of its popularity because of its usefulness in the Scottish Highlands. Besides being capable of eradicating pests that destroyed crops or killed valuable livestock, the Cairn Terrier left to its own devices would even bring home small game animals that were suitable for eating.

Cairns were bred from the same terrier stock that produced other familiar Scottish breeds, such as the similar-looking West Highland White Terrier and the infamous Scottish Terrier or "Scottie". At the turn of the century, all these dogs were grouped together, but after a little over a decade, the American Kennel Club and the Kennel Club of Great Britain both recognized the Cairn Terrier as its own breed with specific standards.

The American Kennel Club's standards for the Cairn Terrier were last emended and solidified in the late 1930s. The AKC sets a minimum weight of fourteen pounds for males and thirteen pounds for females, though a healthy, non-show weight can be anywhere between twelve to eighteen pounds. The height of the Cairn Terrier is similarly specific by AKC standards (with a shoulder height of nine inches for females and ten inches for males), but a shoulder height of anywhere between eight and thirteen inches is acceptable by non-show health standards. With this breed's hyperactivity and love for food, there can be extreme weight variations in either direction that are unhealthy. It is best to closely monitor your Cairn Terrier's weight and make sure to exercise them more if they are getting a little porky or feed them a little more if they are looking thin!

Though the Cairn Terrier is rarely used for its original purpose as a hunting dog today, their instincts and origin clearly shine through in their exuberant little personalities.