What was population of american indians before white peopl came?

Research by some scholars provides population estimates of the pre-contact Americas to be as high as 112 million in 1492, while others estimate the population to have been as low as eight million. In any case, the native population declined to less than six million by 1650.

I believe there is a book on the matter as well. Good luck. :)

The last sentence of the gettysberg address