| Census | Population |
| 1850 | 93,000 |
| 1860 | 380,000 |
| 1870 | 560,000 |
| 1880 | 865,000 |
| 1890 | 1,213,000 |
| 1900 | 1,485,000 |
| 1910 | 2,378,000 |
| 1920 | 3,427,000 |
| 1930 | 5,677,000 |
| 1940 | 6,950,000 |
| 1950 | 10,643,000 |
| 1960 | 15,863,000 |
| 1970 | 20,039,000 |
| 1980 | 23,780,000 |
| 1990 | 29,558,000 | 2000 | 48,977,000 |