Warren County Population 2018
Warren County's estimated population is 17,167 with a growth rate of -0.81% in the past year according to the most recent United States census data. Warren County is the 62nd largest county in Illinois.
| Year | Population | Growth | Growth Rate |
| 2017 | 17,167 | -140 | -0.81% |
| 2016 | 17,307 | -63 | -0.36% |
| 2015 | 17,370 | -286 | -1.62% |
| 2014 | 17,656 | 13 | 0.07% |
| 2013 | 17,643 | -96 | -0.54% |
| 2012 | 17,739 | -94 | -0.53% |
| 2011 | 17,833 | 114 | 0.64% |
| 2010 | 17,719 | -1,462 | -7.62% |
| 1990 | 19,181 | -2,762 | -12.59% |
| 1980 | 21,943 | 348 | 1.61% |
| 1970 | 21,595 | 8 | 0.04% |
| 1960 | 21,587 | -394 | -1.79% |
| 1950 | 21,981 | 695 | 3.27% |
| 1940 | 21,286 | -459 | -2.11% |
| 1930 | 21,745 | 257 | 1.20% |
| 1920 | 21,488 | -1,825 | -7.83% |
| 1910 | 23,313 | 150 | 0.65% |
| 1900 | 23,163 | 1,882 | 8.84% |
| 1890 | 21,281 | -1,652 | -7.20% |
| 1880 | 22,933 | -241 | -1.04% |
| 1870 | 23,174 | 4,838 | 26.39% |
| 1860 | 18,336 | 10,160 | 124.27% |
| 1850 | 8,176 | 1,437 | 21.32% |
| 1840 | 6,739 | 6,431 | 2087.99% |
| 1830 | 308 | 0.00% |