Historic Whitetail Deer Population

UF Research: Total Historic Deer Population November 28, 2000 Science Daily
... experts believe the population of [white-tail] deer in the United States is about equal to what it was before Europeans arrived, with somewhere between 24 million and 34 million nationwide. That's up from just 350,000 in 1900, when the population crashed largely because of unregulated hunting...
In 1890 the U.S. BIological Survey estimated the whitetail population at 300,000. 

Deer Can Be Too Many, Too Few, or Just Enough for Healthy Forests. Spring, 2012, No. 16
... "Deer populations at the time of European settlement in areas of “prime habitat” (3 million square miles) ranged from 8 to 20 per square mile" ...
[at the average of 14 per square mile and 3 million square miles of habitat:  14 X 3,00,000 = 42,00,000 or 42 million deer, consistent with the estimate on the graph}