The history of the United States has been an experiment in democracy for more than 200 years. Issues that were addressed in the early years continue to be addressed and resolved today: big government versus small government, individual rights versus group rights, unfettered capitalism versus regulated commerce and labor, engagement with the world versus isolationism. The expectations for American democracy have always been high, and the reality has sometimes been disappointing. Yet the nation has grown and prospered, through a continual process of adaptation and compromise.

At the height of the most recent Ice Age, about 35,000 years ago, much of the world's water was locked up in vast continental ice sheets. A land bridge as much as 1,500 kilometers wide connected Asia and North America. By 12,000 years ago, humans were living throughout much of the Western Hemisphere.

The first Americans crossed the land bridge from Asia and were believed to have stayed in what is now Alaska for thousands of years. They then moved south into the land that was to become the United States. They settled along the Pacific Ocean in the Northwest, in the mountains and deserts of the Southwest, and along the Mississippi River in the Middle West.

These early groups are known as Hohokam, Adenans, Hopewellians, and Anasazi. They built villages and grew crops. Some built mounds of earth in the shapes of pyramids, birds, or serpents. Their life was closely tied to the land, and their society was clan-oriented and communal. Elements of the natural world played an essential part in their spiritual beliefs. Their culture was primarily oral, although some developed a type of hieroglyphics to preserve certain texts. Evidence shows that there was a good deal of trade among the groups but also that some of their relations were hostile.

For reasons not yet completely understood, these early groups disappeared over time and were replaced by other groups of Native Americans, including Hopi and Zuni, who flourished. By the time Europeans reached what is now the United States, about two million native people, maybe more, lived here.

The first Europeans to arrive in North America — at least the first for whom there is solid evidence — were Norse. They traveled west from Greenland, where Erik the Red had founded a settlement around the year 985. In 1001, his son Leif is thought to have explored the northeast coast of what is now Canada. Ruins of Norse houses dating from that time have been discovered at L'Anse-aux-Meadows in northern Newfoundland.

It would be almost 500 more years before other Europeans reached North America and another 100 years after that before permanent settlements were established. The first explorers were searching for a sea passage to Asia. Others — chiefly British, Dutch, French, and Spanish — came later to claim the lands and riches of what they called the "New World."

The first and most famous of these explorers was Christopher Columbus of Genoa. His trips were financed by Queen Isabella of Spain. Columbus landed on islands in the Caribbean Sea in 1492, but he never saw the mainland of the future United States. John Cabot of Venice came five years later on a mission for the king of England. His journey was quickly forgotten, but it provided the basis for British claims to North America.