| Year | Northeast | Midwest | South | West |
| regional population, in millions | ||||
| 1900 | 21.047 | 26.333 | 24.524 | 4.309 |
| 1910 | 25.869 | 29.889 | 29.389 | 7.082 |
| 1920 | 29.662 | 34.020 | 33.126 | 9.214 |
| 1930 | 34.427 | 38.594 | 37.858 | 12.324 |
| 1940 | 35.977 | 40.143 | 41.666 | 14.379 |
| 1950 | 39.478 | 44.461 | 47.197 | 20.190 |
| 1960 | 44.678 | 51.619 | 54.973 | 28.053 |
| 1970 | 49.061 | 56.590 | 62.813 | 34.838 |
| 1980 | 49.137 | 58.867 | 75.367 | 43.171 |
| 1990 | 50.809 | 59.669 | 85.446 | 52.786 |
| 1999 | 51.830 | 63.242 | 96.469 | 61.150 |
Sources: U.S. Department of Commerce, Bureau of the Census, 1990 Census of Population and Housing, CPH-2-1 (GPO, Washington, DC, 1993).
--, State Population Estimates: Annual Time Series July 1, 1990 to July 1, 1999 (an Internet accessible data file; release date: December 29, 1999).
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