Built on an island in Lake Texoco in the early fourteenth century, the Aztec city of Tenochtitln was the largest city in the Americas. Rebuilt after the Spanish conquest, Mexico City served as the political, administrative and financial centre of a major part of the colonial empire of Spain. During the latter part of the nineteenth century, Mexico City modernized rapidly. The industrial development of the city was facilitated by the fact that it had the best infrastructure of the country, the largest consumer market, and a relatively well-trained labour force.
Due to the devastation of the smallpox epidemic in 1520, Mexico City began its existence with only 30,000 people. Over the next four centuries population levels grew slowly until the spectacular growth of the twentieth century. Migration was more important than natural increase in fueling the population growth in Mexico City. From a population of 1.6 million in 1940, it increased to 3.1 million in 1950, 5.4 million in 1960, 9.1 million in 1970, 13.9 million in 1980, and about 15.6 million in 1995. This rapid growth in Mexico City was the outcome of policies that greatly favoured the concentration of industrial production in Mexico City. Mexico City had access to electricity, oil and other power sources, the provision of water and drainage facilities, and was the focus of major road investment programmes. The most important industrial activities undertaken in the city include the manufacture of clothing, furniture and repairs, publishing activities, production of rubber, plastic and metal goods, as well as the assembly and repair of electrical goods. Most of this production was for the national and local markets rather than oriented towards global markets, as is now the case due to the North American Free Trade Agreement. Urbanization has had a serious negative effect on the ecosystem of Mexico City. Though water supplies have increased to 300 liters per day per capita, the city lacks an efficient distribution system. Although 80% of the population have piped inside plumbing, residents in the peripheral areas cannot access the sewage network and a great percentage of waste-water remains untreated as it passes to the north for use as irrigation water. Pollution is undoubtedly the most serious problem in Mexico City. 2.6 million private automobiles in the city were estimated to be responsible for 50% of traffic congestion and produced about 80% of air pollution. Though government planning strategies strive towards the decentralization of Mexico City, tax subsidies and other government actions often make the city more attractive than other areas. Furthermore, Mexicans who desire to remain in Mexico City are influenced by numerous social, political, educational and cultural factor, and they often equate living in Mexico City with the image of personal success. It seems unlikely, therefore, that the national predominance of Mexico City will change very much during the remainder of the twentieth century.