| Population Change 1990-2000 | ||||
| County or Municipality | 2000 Population | 1990 Population | Population Change | Percent Change |
| Pennsylvania | 12 281 054 | 11 881 643 | 399 411 | 3.4 |
| Greene County | 40 672 | 39 550 | 1 122 | 2.8 |
| Aleppo township | 597 | 656 | - 59 | - 9.0 |
| Carmichaels borough | 556 | 532 | 24 | 4.5 |
| Center township | 1 393 | 1 460 | - 67 | - 4.6 |
| Clarksville borough | 234 | 211 | 23 | 10.9 |
| Cumberland township | 6 564 | 6 742 | - 178 | - 2.6 |
| Dunkard township | 2 358 | 2 386 | - 28 | - 1.2 |
| Franklin township | 7 694 | 5 562 | 2 132 | 38.3 |
| Freeport township | 302 | 327 | - 25 | - 7.6 |
| Gilmore township | 295 | 365 | - 70 | - 19.2 |
| Gray township | 236 | 220 | 16 | 7.3 |
| Greene township | 445 | 494 | - 49 | - 9.9 |
| Greensboro borough | 295 | 307 | - 12 | - 3.9 |
| Jackson township | 516 | 546 | - 30 | - 5.5 |
| Jefferson borough | 337 | 355 | - 18 | - 5.1 |
| Jefferson township | 2 528 | 2 536 | - 8 | - 0.3 |
| Monongahela township | 1 714 | 1 858 | - 144 | - 7.8 |
| Morgan township | 2 600 | 2 887 | - 287 | - 9.9 |
| Morris township | 1 040 | 898 | 142 | 15.8 |
| Perry township | 1 720 | 1 719 | 1 | 0.1 |
| Rices Landing borough | 443 | 457 | - 14 | - 3.1 |
| Richhill township | 1 062 | 1 102 | - 40 | - 3.6 |
| Springhill township | 476 | 506 | - 30 | - 5.9 |
| Washington township | 1 106 | 1 071 | 35 | 3.3 |
| Wayne township | 1 223 | 1 317 | - 94 | - 7.1 |
| Waynesburg borough | 4 184 | 4 270 | - 86 | - 2.0 |
| Whiteley township | 754 | 766 | - 12 | - 1.6 |
| Source: U.S. Census Bureau | Prepared by: Pennsylvania State Data Center | |||