Chihuahua. History: The Chihuahua is considered the smallest purebred dog in the world and bears the name of the largest state of the Republic of Mexico (Chihuahua). It is thought that this dog once lived in the wild and was captured and tamed by the natives at the time of the Toltec civilization. Some representations of a small dog called “Techichi” that lived in the Tula region appeared in the decoration of architectural elements. These statues closely resemble the current Chihuahuas. General Appearance: Compact built dog. The most peculiar characteristic is its apple-shaped skull and the way it holds its tail, which is moderately long, very high, both curved and rounded in a semicircle with the tip pointing towards the lumbar region.