The smallest breed of dog is the Chihuahua. It is named after a region in Mexico with the same name. Chihuahuas were believed to be descendants of Techichi, a slightly larger breed that was associated with Aztec royalty. However, most people now think that Spanish merchants brought Chihuahuas to Spain through trading with China and then eventually brought them to Mexico. Chihuahuas were then brought to the United States by those who visited Mexico.