Agricultural settlements dated to about 500 BCE have been found in the San Juan del Río and Huimilpan areas, which was during the Teotihuacan era. The ancient city had interest and influence in the area because of its agriculture, but did not dominate it. After the fall of this city, the Querétero area had its highest rate of development of both agriculture and social structure. The area was inhabited early on by a number of ethnicities, including the Otomi, Toltecs, Chichimecas, Purépechas and Mexicas. In the 10th century, the area experience population shifts which did not stabilize until the 12th century. Much of this migration moved south from the Querétaro area into the Valley of Mexico. Those who remained by the end of the 12th century were mostly in hunter-gatherer communities and small agricultural settlements. The region’s agriculture and minerals continued to attract the interest of more powerful neighbors. In the 15th century, both the Aztec Empire and Purépecha Empire had strong influence parts of the state, especially in the south, but would never incorporate the area completely into either empire. The Aztec’s interest in the area was mostly to use it as a bulwark against marauding northern Chichimeca tribes, and it never became a tributary state. During this time, as well, a number of new peoples entered the state, most likely from the north, primarily the Pames and the Chichimeca Jonaz. The first group practiced agriculture in the valleys and the latter in the mountain areas.