Precolonial Population Density in the Americas

Bruhn and Gallego (2012) compile population density data in the Americas before European colonization. Their primary source is

Denevan, William M. (Ed.), The Native Population of the Americas in 1492, 2nd ed. (Madison: University of Wisconsin Press, 1992),

but they augment this data with various other sources. See Appendix C of their paper for detail.