Encyclopædia Britannica, Ninth Edition/Aztecs
AZTECS, the native name of one of the tribes that occupied the table-land of Mexico on the arrival of the Spaniards in America. It has been very frequently employed as equivalent to the collective national title of Nahuatlecas, or Mexicans. The Aztecs came, according to native tradition, from a country to which they gave the name of Aztlan, usually supposed to lie towards the N.W., but the satisfactory localisation of it is one of the greatest difficulties in Mexican history. The date of the exodus from Aztlan is equally undetermined, being fixed by various authorities in the llth and by others in the 12th century. One Mexican manuscript gives a date equivalent to 1164 A.D. They gradually increased their influence among other tribes, until, by union with the Toltecs, who occupied the table-land before them, they extended their empire to an area of from 18,000 to 20,000 square leagues. The researches of Humboldt gave the first clear insight into the early periods of their history. See Mexico.