Jefferson County's 2026 population is estimated at 18,382, reflecting a 0.14% growth rate over the past year (World Population Review estimate based on U.S. Census Bureau data). Jefferson County is the 30th largest county in Kansas. The 2010 population was 19,120 and has grown -3.86% since 2010.
Data after 2023 is projected based on recent change
Overall: 44.2 years
Female: 44.4 years
Male: 44.1 years
There are 14,316 adults, (3,666 of whom are seniors) in Jefferson County.
Female: 9,064 (49.4%)
Male: 9,285 (50.6%)
The racial composition of Jefferson County includes 92.54% White, and smaller percentages for Black or African American, Native American, other race, Asian, Native Hawaiian or Pacific Islander and multiracial populations.
| Race | Population ↓ | Percentage (of total) |
|---|---|---|
| White | 16,980 | 92.54% |
| Two or more races | 1,044 | 5.69% |
| Black or African American | 111 | 0.6% |
| Native American | 92 | 0.5% |
| Other race | 74 | 0.4% |
| Asian | 45 | 0.25% |
| Native Hawaiian or Pacific Islander | 3 | 0.02% |
Jefferson County 's average per capita income is $53,001. Household income levels show a median of $81,278. The poverty rate stands at 5.64%.
| Name | Median ↓ | Mean |
|---|---|---|
| Married Families | $109,262 | - |
| Families | $100,625 | $118,982 |
| Households | $81,278 | $100,809 |
| Non Families | $43,238 | $54,120 |
Average Income
Median Household Income
Poverty Rate
