Did the Expansion of the Aztec Empire Lead to Their Downfall? The Aztec Indians originated from a place called Aztlan, somewhere in north or northwest Mexico. At that time the Aztecs were a small, nomadic tribe living in the border territory on the margins of civilized Mesoamerica. (see map I) In the 13th century they settled in the valley of central Mexico. The Aztecs finally found refuge on a small island in Lake Texcoco, where about 1345, they founded the town of Tenochtitlan. The island was found through a prophecy which said they would settle where they found an eagle perched on a cactus. (see diagram I) During the next century the Aztecs