In early first century CE, Teotihuacan was just a hamlet. Its population then grew as people from the Valley of Mexico began arriving there. With a larger labor force at its disposal, the local rulers grew richer and devised a master plan for a new city with the great building projects of the pyramids of the sun and the moon. The plan was inspired by the Aztec conception of the universe, and indeed, as the place where the universe itself originated. It also made Teotihuacan the grandest city in Mesoamerica during the Classic Period.
Teotihuacan's control of the obsidian mines at Otumba and Pachuca allowed it to centralize the production of obsidian goods, some for domestic sale, the rest for export. With this, and its monopoly on the distribution of Thin Orange pottery, Teotihuacan developed a trading system that embraced almost every region of Mesoamerica, including places as far away as the Maya area, the modern state of Guerrero, and the area around the Gulf of Mexico.
Teotihuacan's metropolitan feel, its trading system, and the religious prestige it accrued from its giant pyramids and related ceremonies, attracted a floating population that enriched the quality of life in the great city. At its peak between 150—450 CE, it stretched over 30 square km and had a population of between 150,000 and 250,000.
After flourishing for centuries, Teotihuacan collapsed c. 750 CE, partly due to adverse pressures from the new population centers that sprang up on the Mexican plateau. However, evidence of fire, and the systematic, devastating ways in which the buildings lining the Avenue of the Dead were destroyed point to the main cause of its collapse being internal rebellions. [—Preceding text adapted from a display at the Museo Nacional de Antropologia (Mexico pics).]
Here is a ten minute video from my second trip to Teotihuacan in July 2002, along with Mexico City footage from the Zocalo, Plaza Garibaldi, and the excellent Museo Nacional de Antropologia, which contains many artifacts from Teotihuacan.
