| Historical populations | |||
|---|---|---|---|
| Census | Pop. | %± | |
| 1840 | 4,470 | ||
| 1850 | 29,963 | 570.3% | |
| 1860 | 112,172 | 274.4% | |
| 1870 | 298,977 | 166.5% | |
| 1880 | 503,185 | 68.3% | |
| 1890 | 1,099,850 | 118.6% | |
| 1900 | 1,698,575 | 54.4% | |
| 1910 | 2,185,283 | 28.7% | |
| 1920 | 2,701,705 | 23.6% | |
| 1930 | 3,376,438 | 25.0% | |
| 1940 | 3,396,808 | 0.6% | |
| 1950 | 3,620,962 | 6.6% | |
| 1960 | 3,550,404 | −1.9% | |
| 1970 | 3,366,957 | −5.2% | |
| 1980 | 3,005,072 | −10.7% | |
| 1990 | 2,783,911 | −7.4% | |
| 2000 | 2,893,666 | 3.9% | |
| 2010 | 2,695,598 | −6.8% | |