Chac Mool sculpture at Chichen Itza, Yucatan, Mexico. Chichén was founded about 6th Century CE, presumably by Maya peoples of the Yucatán Peninsula who had occupied the region since Pre-Classic or Formative, Period (1500 BC – 300 CE).

The main early buildings are in an architectural style known as Puuc, which shows a number of divergences from the styles of the southern lowlands. These earliest structures are to the south of the Main Plaza.

There is evidence that, in 10th Century CE, after the collapse of the Maya cities of the southern lowlands, Chichén was invaded by foreigners, probably Maya speakers who had been strongly influenced by and perhaps were under the direction of Toltec of central Mexico. These invaders may have been the Itzá for whom the site is named; some authorities, however, believe the Itzá arrived 200 to 300 years later.