Following a preface by Brinkley on the importance of critical thinking in the study of history, American History opens with the first years of human settlement in what is now North America. The Clovis people are believed to have crossed the Bering Strait land bridge from Mongolia between 11,000 and13,000 years ago and dispersed across the continent. This group is considered the ancestor of all Indigenous groups in the Americas. However, recent research suggests that other groups arrived by sea much earlier than the Clovis people. Updates in DNA analysis within archaeology have found various unrelated population groups, indicating migration from parts of Asia nowhere near the Bering Strait and perhaps even prehistoric migration from Europe or Africa. New archaeological finds are constantly improving our picture of what early migration to the Americas looked like. Regardless, evidence indicates that the Clovis people were incredibly successful at adapting to life in their new habitat and they eventually dominated the genetic and cultural landscape of North America.

At the peak of the Middle Ages in Europe during the 14th-16th centuries, large empires began on the American continents: the Inca in Peru and the Aztec Mexico. These groups developed advanced technologies like road systems, aqueducts, and complex systems of government—and conquered smaller, less developed societies, many of which willingly aligned themselves with Inca or Aztec leaders to reap their civilization’s benefits.