Fergus County Population 2018
Fergus County's estimated population is 11,291 with a growth rate of -0.08% in the past year according to the most recent United States census data. Fergus County is the 18th largest county in Montana.
| Year | Population | Growth | Growth Rate |
| 2017 | 11,291 | -9 | -0.08% |
| 2016 | 11,300 | 15 | 0.13% |
| 2015 | 11,285 | -26 | -0.23% |
| 2014 | 11,311 | -139 | -1.21% |
| 2013 | 11,450 | 64 | 0.56% |
| 2012 | 11,386 | -68 | -0.59% |
| 2011 | 11,454 | -126 | -1.09% |
| 2010 | 11,580 | -503 | -4.16% |
| 1990 | 12,083 | -993 | -7.59% |
| 1980 | 13,076 | 465 | 3.69% |
| 1970 | 12,611 | -1,407 | -10.04% |
| 1960 | 14,018 | 3 | 0.02% |
| 1950 | 14,015 | -25 | -0.18% |
| 1940 | 14,040 | -2,491 | -15.07% |
| 1930 | 16,531 | -11,813 | -41.68% |
| 1920 | 28,344 | 10,959 | 63.04% |
| 1910 | 17,385 | 10,448 | 150.61% |
| 1900 | 6,937 | 3,423 | 97.41% |
| 1890 | 3,514 | 0.00% |