Warren County Population 2018
Warren County's estimated population is 39,659 with a growth rate of -0.85% in the past year according to the most recent United States census data. Warren County is the 55th largest county in Pennsylvania.
| Year | Population | Growth | Growth Rate |
| 2017 | 39,659 | -339 | -0.85% |
| 2016 | 39,998 | -376 | -0.93% |
| 2015 | 40,374 | -336 | -0.83% |
| 2014 | 40,710 | -272 | -0.66% |
| 2013 | 40,982 | -280 | -0.68% |
| 2012 | 41,262 | -240 | -0.58% |
| 2011 | 41,502 | -273 | -0.65% |
| 2010 | 41,775 | -3,275 | -7.27% |
| 1990 | 45,050 | -2,399 | -5.06% |
| 1980 | 47,449 | -233 | -0.49% |
| 1970 | 47,682 | 2,100 | 4.61% |
| 1960 | 45,582 | 2,884 | 6.75% |
| 1950 | 42,698 | -91 | -0.21% |
| 1940 | 42,789 | 1,336 | 3.22% |
| 1930 | 41,453 | 1,429 | 3.57% |
| 1920 | 40,024 | 451 | 1.14% |
| 1910 | 39,573 | 627 | 1.61% |
| 1900 | 38,946 | 1,262 | 3.35% |
| 1890 | 37,684 | 9,703 | 34.68% |
| 1880 | 27,981 | 4,084 | 17.09% |
| 1870 | 23,897 | 4,707 | 24.53% |
| 1860 | 19,190 | 5,519 | 40.37% |
| 1850 | 13,671 | 4,393 | 47.35% |
| 1840 | 9,278 | 4,581 | 97.53% |
| 1830 | 4,697 | 2,721 | 137.70% |
| 1820 | 1,976 | 1,149 | 138.94% |
| 1810 | 827 | 594 | 254.94% |
| 1800 | 233 | 0.00% |