Clay County, Iowa Population 2019
Clay County, Iowa's estimated population is 16,153 with a growth rate of -0.88% in the past year according to the most recent United States census data. Clay County, Iowa is the 48th largest county in Iowa.
| Year | Population | Growth | Growth Rate |
| 2018 | 16,134 | -19 | -0.12% |
| 2017 | 16,153 | -143 | -0.88% |
| 2016 | 16,296 | -201 | -1.22% |
| 2015 | 16,497 | 12 | 0.07% |
| 2014 | 16,485 | 45 | 0.27% |
| 2013 | 16,440 | -99 | -0.60% |
| 2012 | 16,539 | -56 | -0.34% |
| 2011 | 16,595 | -40 | -0.24% |
| 2010 | 16,635 | -950 | -5.40% |
| 1990 | 17,585 | -1,991 | -10.17% |
| 1980 | 19,576 | 1,112 | 6.02% |
| 1970 | 18,464 | -40 | -0.22% |
| 1960 | 18,504 | 401 | 2.22% |
| 1950 | 18,103 | 341 | 1.92% |
| 1940 | 17,762 | 1,655 | 10.28% |
| 1930 | 16,107 | 447 | 2.85% |
| 1920 | 15,660 | 2,894 | 22.67% |
| 1910 | 12,766 | -635 | -4.74% |
| 1900 | 13,401 | 4,092 | 43.96% |
| 1890 | 9,309 | 5,061 | 119.14% |
| 1880 | 4,248 | 2,725 | 178.92% |
| 1870 | 1,523 | 1,471 | 2828.85% |
| 1860 | 52 | 0.00% |