History: Collectively, the people of the allied Central Mexican and American city states between the 12th century CE (AD) and the 15th century Spanish invasion are commonly referred to as the Aztecs. The Aztec empire was controlled primarily by a political body called the Triple Alliance, made up of the Acolhua people of Texcoco, the Mexica in Tenochtitlán, and the Tepaneca people of Tlacopan. These three peoples, and three cities, were responsible for the domination of much of Mexico during the period. The Aztec capital city was located at Tenochtitlán, which is the site of the modern Mexico city, and their empire covered nearly all of the current country of Mexico, extending down into other regions of Central America as well. Over time, Tenochtitlán became the primary city of the Triple Alliance, and the Mexica became the rulers of the empire. Social stratification was significant, and religion played an important role in the spiritual and political life of the people.