Scholarly estimates have run from 8 million to 112 million. Europe, by way of comparison, had about 70 million people at the time.
In the 1830s artist George Catlin estimated there had been 16 million Indians in North America at the time of contact. He was in the minority. In 1894, the Census Bureau suggested the number had been more like 600,000.
In the 20th century experts used counts at the time of contact (as reported by explorers, etc.) to estimate the pre-contact population. In 1928, Smithsonian ethnologist James Mooney guessed 1.15 million persons were present in 1492 in what is now the U.S. and Canada. Anthropologist Alfred Kroeber further refined Mooney’s work and concluded there were 4.2 million inhabitants in North America and 4.2 million inhabitants in South America before Columbus.
The problem with these estimates is that, among other things, they failed to account for the incredible loss of life due to disease BEFORE direct contact; that is, before the explorers and first settlers could make a count. Diseases unknown in the Americas (foremost being smallpox) may have killed as many as 90 percent of the indigenous people in some areas BEFORE any Europeans arrived.
In the past 40 years the estimates of indigenous population have been much higher than before (and much higher than what most of us learned in school). In 1966, anthropologist Henry Dobyns calculated there had been more than 10 million Indians in North America and 112 million altogether. Most critics felt he oversimplified (and overestimated the loss to disease). Subsequent estimates have moderated Dobyns’s count, but have been much higher than those that preceded him.
In the 1990s, geographer William Denevan attempted to reconcile various estimates. He concluded there were about 54 million people in the hemisphere; 3.8 million of these were in what is now the U.S. and Canada.
Interesting. I’ve also read that back then, as now, California had about 12-15% of the total population of what is now the USA.
The California Indian population suffered some of the worst genocide in history. European immigrants rode around in bands and simply killed every Indian they could find.
From the Encyclopedia of North American Indians Houghton Mifflin:
Government Indian policies in California rarely resembled those in other parts of North America. In 1850, the new California legislature passed the Government and Protection of the Indians Act, which provided for the indenture of loitering, intoxicated, or orphaned Indians and regulated Indian employment. The law was amended ten years later to expand the scope of slavery to include adults. The state policy resembled the “black codes” adopted by slave states as a means to control both free blacks and bondsmen. The state government also subsidized military campaigns against Indians, allowing for the indiscriminate killing of Indian women and children, as well as men, and justifying the slaughter as protecting settlers from Indian threat. A program of genocide, called “extermination” in the California press, was carried out by a group calling itself the California Volunteer Militia and by temporary bands of miners and ranchers?all organized for the purpose of killing Indians. Between 1845 and 1870, the Indian population in California declined by 80 percent, from 150,000 to 30,000 people. As many as 40 percent of these deaths were the result of extermination killings. Only a few native Californians survived the removal and extermination campaigns of the 1850s. These survivors found an uneasy refuge at the seven military reservations created to protect them. California operated the reservation system beginning in 1853, when Congress appropriated $250,000 to establish the first five reservations; all the reservations were closed in 1864. Later, Congress passed the Four Reservation Act, which authorized the creation of the Hoopa Valley, Tule River, and Round Valley reserves in California (no fourth reservation was ever completed).
Where there are rich resources, there will be mass killings, always has always will.
On a side note: a great book that helps explain how the early Europeans conquered the world via biology rather than military might is “Ecological Imperialism” by Alfred Crosby