Main article: Pre-Columbian
The earliest known inhabitants of what is now the United States are thought to have arrived in Alaska by crossing the Bering land bridge, at least 14,000 30,000 years ago. Some of these groups migrated south and east, and over time spread throughout the Americas. These were the ancestors to modern Native Americans in the United States and Alaskan Native peoples, as well as all indigenous peoples of the Americas.
Many indigenous peoples were semi-nomadic tribes of hunter-gatherers; others were sedentary and agricultural civilizations. Many formed new tribes or confederations in response to European colonization. Well-known groups included the Huron, Apache Tribe, Cherokee, Sioux, Delaware, Algonquin, Choctaw, Mohegan, Iroquois (which included the Mohawk nation, Oneida tribe, Seneca nation, Cayuga nation, Onondaga and later the Tuscarora tribe) and Inuit. Though not as technologically advanced as the Mesoamerican civilizations further south, there were extensive pre-Columbian sedentary societies in what is now the US. The Iroquois had a politically advanced and unique social structure that was at the very least inspirational if not directly influential to the later development of the democratic United States government, a departure from the strong monarchies from which the Europeans came.
 North America's Moundbuilder Culture
A Mississippian priest, with a ceremonial flint mace. Artist Herb Roe, based on a repousse copper plate.Mound Builder is a general term referring to the American Indians who constructed various styles of earthen mounds for burial, residential and ceremonial purposes. These included Archaic, Woodland period (Adena and Hopewell cultures), and Mississippian period Pre-Columbian cultures dating from roughly 3000 BC to the 16th century AD, and living in the Great Lakes region, the Ohio River region, and the Mississippi River region.
Mound builder cultures can be divided into roughly three eras:
Poverty Point in what is now Louisiana is perhaps the most prominent example of early archaic mound builder construction (c. 2500 1000 BC). An even earlier example, Watson Brake, dates to approximately 3400 BC and coincides with the emergence of social complexity worldwide.
The Archaic period was followed by the Woodland period (c. 1000 BC). Some well-understood examples would be the Adena culture of Ohio and nearby states and the subsequent Hopewell culture known from Illinois to Ohio and renowned for their geometric earthworks. The Adena and Hopewell were not, however, the only mound building peoples during this time period. There were contemporaneous mound building cultures throughout the Eastern United States.
Main article: Mississippian Culture
Around 900 1450 AD the Mississippian culture developed and spread through the Eastern United States, primarily along the river valleys. The location where the Mississippian culture is first clearly developed is located in Illinois, and is referred to today as Cahokia.
 Colonial period
Main article: Colonial history of the United States
The Mayflower, which transported Pilgrims to the New WorldAfter a period of exploration by people from various European countries, Spanish, Dutch, English, French, Swedish, and Portuguese settlements were established. Christopher Columbus was the first European to set foot on what would one day become U.S. territory when he came to Puerto Rico on November 19, 1493, during his second voyage. In the 15th century, Europeans brought horses, cattle, and hogs to the Americas and, in turn, took back to Europe corn, potatoes, tobacco, beans, and squash.
 Spanish colonization
Coronado Sets Out to the North (1540) by Frederic Remington, oil on canvas, 1905.See also: New Spain Spanish explorers came to what is now the United States beginning with...