Winnebago County Population 2018
Winnebago County's estimated population is 284,778 with a growth rate of -0.46% in the past year according to the most recent United States census data. Winnebago County is the 7th largest county in Illinois.
| Year | Population | Growth | Growth Rate |
| 2017 | 284,778 | -1,310 | -0.46% |
| 2016 | 286,088 | -1,053 | -0.37% |
| 2015 | 287,141 | -1,529 | -0.53% |
| 2014 | 288,670 | -2,213 | -0.76% |
| 2013 | 290,883 | -1,166 | -0.40% |
| 2012 | 292,049 | -1,522 | -0.52% |
| 2011 | 293,571 | -1,517 | -0.51% |
| 2010 | 295,088 | 42,175 | 16.68% |
| 1990 | 252,913 | 2,029 | 0.81% |
| 1980 | 250,884 | 4,261 | 1.73% |
| 1970 | 246,623 | 36,858 | 17.57% |
| 1960 | 209,765 | 57,380 | 37.65% |
| 1950 | 152,385 | 31,207 | 25.75% |
| 1940 | 121,178 | 3,805 | 3.24% |
| 1930 | 117,373 | 26,444 | 29.08% |
| 1920 | 90,929 | 27,776 | 43.98% |
| 1910 | 63,153 | 15,308 | 31.99% |
| 1900 | 47,845 | 7,907 | 19.80% |
| 1890 | 39,938 | 9,433 | 30.92% |
| 1880 | 30,505 | 1,204 | 4.11% |
| 1870 | 29,301 | 4,810 | 19.64% |
| 1860 | 24,491 | 12,718 | 108.03% |
| 1850 | 11,773 | 7,164 | 155.44% |
| 1840 | 4,609 | 0.00% |