The modern short-haired Chihuahua originated in Chihuahua, Mexico, in the 1850s. The breed's ancient origins are debated, but historians believe Chihuahuas were first discovered in Mexico, Central America or South America.
One theory suggests Chihuahuas are descended from the South American Techichi dog, which was depicted in Toltec carvings from the ninth century. Illustrations of Techichis portrayed characteristics similar to Chihuahuas, including their round heads and big ears. The Techichi population was assimilated into Aztec culture after the Toltecs were conquered, but it gradually dwindled during Spanish conquest. The Aztecs believed Techichi dogs were clairvoyant underworld guides and praised them as symbols of mysticism and healing.