Much of the Toluca Valley was probably part of the earlier Tepanec Empire, based in Azcapotzalco, with its height around 1370. A number of Toluca Valley towns are listed as Tepenac vassals. The historic record in regards to pre-Aztec Toluca area is not clear because the Aztec destroyed many documents and, from 1428 to 1470, Toluca Valley settlements do not figure prominently in Aztec records. The names of both Tollocan (Toluca) and Matlatzinco apparently are used in records to refer to the same area, but it is not known if they referred to the same city/state. By the eve of the Aztec conquest in 1475, it is clear that they were two different city-states.