Maize, unknown outside the New World, is extensively cultivated in all its present forms by the indigenous peoples of North and South America.

Nuclear American peoples, now almost entirely reliant on cultivation, have domesticated hundreds of species of plants for use not only as foods, but also as raw materials (such as pima cotton), as poisons, and as hallucinogens and stimulants.

Domesticated plants and agricultural techniques have gradually spread to other parts of the Americas, although most other New World cultivators, such as those in the tropical forest of South America and in the Southeast and Southwest of North America, continue to supplement cultivation with ancient food-collecting techniques.

At the time of contact between Old World and New, the area of the future United States has a population averaging only about one person per thirteen to twenty-six square kilometers (roughly one person per five to ten square miles).