Polk County Population 2018
Polk County's estimated population is 481,830 with a growth rate of 1.49% in the past year according to the most recent United States census data. Polk County is the 1st largest county in Iowa.
| Year | Population | Growth | Growth Rate |
| 2017 | 481,830 | 7,062 | 1.49% |
| 2016 | 474,768 | 7,516 | 1.61% |
| 2015 | 467,252 | 6,959 | 1.51% |
| 2014 | 460,293 | 8,261 | 1.83% |
| 2013 | 452,032 | 7,730 | 1.74% |
| 2012 | 444,302 | 6,165 | 1.41% |
| 2011 | 438,137 | 5,914 | 1.37% |
| 2010 | 432,223 | 105,083 | 32.12% |
| 1990 | 327,140 | 23,970 | 7.91% |
| 1980 | 303,170 | 17,069 | 5.97% |
| 1970 | 286,101 | 19,786 | 7.43% |
| 1960 | 266,315 | 40,305 | 17.83% |
| 1950 | 226,010 | 30,175 | 15.41% |
| 1940 | 195,835 | 22,998 | 13.31% |
| 1930 | 172,837 | 18,808 | 12.21% |
| 1920 | 154,029 | 43,591 | 39.47% |
| 1910 | 110,438 | 27,814 | 33.66% |
| 1900 | 82,624 | 17,214 | 26.32% |
| 1890 | 65,410 | 23,015 | 54.29% |
| 1880 | 42,395 | 14,538 | 52.19% |
| 1870 | 27,857 | 16,232 | 139.63% |
| 1860 | 11,625 | 7,112 | 157.59% |
| 1850 | 4,513 | 0.00% |