The Aztec empire
The Aztecs (1300) were the youngest of the Big Three American Indian empires. As the northernmost empire in Mesoamerica, the Aztec developed around modern-day Mexico City in about 1,300 CE, ruling for about 200 years before Hernan Cortez and his Spanish army arrived to take over their empire. Mexico City was a city in the middle of a lake, with beautiful temples built along canals and a system of floating island gardens that fed much of the population.
Mexico City was connected with its provinces and tributary states by a system of roads usually maintained through tribute from local rulers. Because the people had no horses or any kind of wheeled vehicles, the roads were intended to facilitate fast foot travel. By order of the Aztecs, travelers had places to rest, eat, and even use a latrine at regular intervals — roughly every five to seven miles. Couriers with messages constantly traveled along those ways, keeping the Aztecs informed of events and reporting whether the roads needed work. Due to this steady surveillance, even women could travel alone — a fact that amazed the Spaniards because lone women hadn't been safe in Europe since the time of the Romans.
The Aztecs were a warlike people with an emperor, nobles, priests, tax collectors, and a merchant middle class. They captured prisoners in constant conflicts and used them for human sacrifices. American Indian enemies of the Aztecs' helped Cortez and his small band of brave and bloodthirsty soldiers conquer the Aztecs and kill their king. This event led to an uprising in Mexico City, from which Cortez barely escaped with his life. Other American Indians were glad to see the Aztecs removed from the complete power they'd enjoyed for only a comparative few years.
Corn cultivation and American Indian civilizations
Corn made all the difference to American Indian civilization. The first planted-corn agriculture occurred in the Mexican highlands in about 5,000 BCE — a full 6,000 years after the first European people got to the New World and around the time large-scale crop-raising got going in Egypt and the Middle East. Corn-growing took 4,000 years to reach the American Southwest, where corn supported an advancing culture 1,000 years before the birth of Christ.
The Anazazis in what's now New Mexico managed to build an apartment house with more than 600 interconnecting rooms. When the Spanish explorers reached the Southwest, they found villages of terraced multistory buildings. (Pueblo, the Spanish word now used for these American Indian settlements and the people who lived in them, means village.)
Two thousand years later, the American Indians in what's now the Eastern United States finally learned to plant corn. In about 1,000 CE, corn helped support a settlement of 25,000 people near modern-day St. Louis, a city twice as big as London at the time. By the time that agriculture got to the eastern section of what's now the United States, the American Indians had only a few hundred years to enjoy cultivation in peace before the arrival of the Europeans.