It is not definitively known how or when the Native Americans first settled the Americas and the present-day United States.
The prevailing theory proposes that people migrated from Eurasia across Beringia, a land bridge that connected Siberia to present-day Alaska during the Ice Age, and then spread southward throughout the Americas over the subsequent generations.
Native Americans, also known as American Indians, Indians, Indigenous Americans and other terms, are the indigenous peoples of the United States.
There are over 500 federally recognized tribes within the US, about half of which are associated with Indian reservations.
Even before the European settlement of what is now the United States, Native Americans suffered high fatalities from contact with new European diseases, to which they had not yet acquired immunity; the diseases were endemic to the Spanish and other Europeans, and spread by direct contact and likely through pigs that escaped from expeditions.
Smallpox epidemics are thought to have caused the greatest loss of life for indigenous populations.
Since the 1960s, Native American self-determination movements have resulted in changes to the lives of Native Americans, though there are still many contemporary issues faced by Native Americans.
After the thirteen colonies revolted against Great Britain and established the United States, President George Washington and Henry Knox conceived of the idea of "civilizing" Native Americans in preparation for assimilation as U. During the 19th century, the ideology of manifest destiny became integral to the American nationalist movement. Congress passed the Indian Removal Act, authorizing the government to relocate Native Americans from their homelands within established states to lands west of the Mississippi River, accommodating European-American expansion.
Expansion of European-American populations to the west after the American Revolution resulted in increasing pressure on Native American lands, warfare between the groups, and rising tensions. This resulted in the ethnic cleansing of many tribes, with the brutal, forced marches coming to be known as The Trail of Tears.
A vast variety of peoples, societies and cultures subsequently developed.
Native Americans were greatly affected by the European colonization of the Americas, which began in 1492, and their population declined precipitously due to introduced diseases, warfare and slavery.