YEAR
e
o
United States
2000
77
1990
75
1980
74
1970
71
1960
70
1950
68
1940
63
1930
60
1920
54
1910
50
1900
47
Free population
1850
39
east coast
1800
36
east coast
1750
30
south
40
north
1700
25
south
50
north
