So this annoyingly helps sustain the myth that North America was an unpopulated forest until being 'settled' by 'settlers'.
1 (http://www.census.gov/history/www/genealogy/decennial_census...):
"Prior to 1900, few Indians are included in the decennial federal census. Indians are not identified in the 1790-1840 censuses. In 1860, Indians living in the general population are identified for the first time. Nearly all of the 1890 census schedules were destroyed as a result of the fire at the Department of Commerce in 1921.
Beginning with the 1900 census, Indians are enumerated on reservations as well as in the general population."
- http://www.census.gov/history/www/genealogy/decennial_census...