When Europeans arrived, perhaps 60 million people occupied the Americas, 7 million of whom lived north of Mexico. In Mesoamerica (present-day Mexico and Guatemala) and the Andes, empires that rivaled the greatest civilizations in world history ruled over millions of people. At the other end of the political spectrum, hunters and gatherers were organized into kin-based bands. Between these extremes, semisedentary societies planted and tended crops in the spring and summer, fished and hunted, made war, and conducted trade. Though we often see this spectrum as a hierarchy in which the empires are most impressive and important while hunter-gatherers deserve scarcely a mention, this bias toward civilizations that left behind monumental architecture and spawned powerful ruling classes is misplaced. Regardless of size or political complexity, the energies and innovations of Native American societies everywhere profoundly transformed American landscapes. To be fully understood, the Americas must be treated in all their complexity, with an appreciation for their diverse societies and cultures.