18,332 people (2024 Census estimate, +0.0% since 2020)
533 square miles of land · 34 people per square mile
“Highest” and “lowest” are just order, not grades: a high rank for poverty or hazard losses means more of it. Each figure's source is in its section below.
18 active community water systems list Jefferson County in the area they serve, reporting 19,964 people served in all (a system that crosses county lines counts its whole population).
| JEFFERSON CO RWD 12 buys surface water · local government · KS2008717 | 3,635 served |
| JEFFERSON CO RWD 3 groundwater · local government · KS2008708 | 2,435 served |
| JEFFERSON CO RWD 1 groundwater · local government · KS2008706 | 2,343 served |
| JEFFERSON CO RWD 13 groundwater · local government · KS2008704 | 2,115 served |
| JEFFERSON CO RWD 7 groundwater · local government · KS2008713 | 1,180 served |
| VALLEY FALLS, CITY OF surface water · local government · KS2008710 | 1,086 served |
| OSKALOOSA, CITY OF buys groundwater · local government · KS2008714 | 1,086 served |
| MCLOUTH, CITY OF groundwater · local government · KS2008702 | 858 served |
Source: U.S. EPA Safe Drinking Water Information System (SDWIS), active community systems, . Look up any system's violations and test results with EPA's search using its ID.
About 18 people were held in Jefferson County's jail, in Vera's latest figure (2021), or 157 per 100,000 residents ages 15–64. In 2016 it was about 29.
Source: Vera Institute of Justice, Incarceration Trends (built from federal Bureau of Justice Statistics jail surveys). Counties without their own jail, or that share one, may show no figure.
6 school districts have their office in Jefferson County. School taxes are usually the largest part of a property tax bill.
Spent $12.6 million — $12.1 million to run schools, about $14,671 per student, plus $368,000 on buildings and equipment. Money in: $2 million local (mostly property tax), $9.7 million state, $898,000 federal.
Spent $11.8 million — $10.9 million to run schools, about $13,955 per student, plus $857,000 on buildings and equipment. Money in: $4.5 million local (mostly property tax), $8.1 million state, $820,000 federal. Long-term debt: $3.2 million.
Spent $9.6 million — $9.5 million to run schools, about $17,074 per student, plus $160,000 on buildings and equipment. Money in: $1.3 million local (mostly property tax), $7.5 million state, $355,000 federal.
Spent $7.3 million — $6.9 million to run schools, about $15,298 per student, plus $266,000 on buildings and equipment. Money in: $1.5 million local (mostly property tax), $5.7 million state, $548,000 federal. Long-term debt: $2.7 million.
Spent $7.1 million — $6.8 million to run schools, about $15,448 per student, plus $236,000 on buildings and equipment. Money in: $1.3 million local (mostly property tax), $6.3 million state, $517,000 federal. Long-term debt: $1.3 million.
Spent $8.1 million — $5.9 million to run schools, about $14,686 per student, plus $2.1 million on buildings and equipment. Money in: $1.3 million local (mostly property tax), $5.1 million state, $297,000 federal. Long-term debt: $4.7 million.
Source: U.S. Census Bureau, 2023 Annual Survey of School System Finances. Districts are listed by the county of their main office; some serve neighboring counties too.
Source: County Health Rankings & Roadmaps 2025 (University of Wisconsin Population Health Institute), which gathers federal data (CDC, Census, and others); measures cover different recent years. Blank lines aren't reported for small counties.
Overall risk: Very Low compared with other U.S. counties. FEMA estimates natural hazards cost Jefferson County about $11.5 million a year on average in buildings, crops and lives. Ability to bounce back (community resilience): Very High; social vulnerability: Very Low.
Source: FEMA National Risk Index (December 2025), expected annual loss. Ratings compare counties nationwide; they're estimates, not predictions.
194 bridges in Jefferson County: 102 in good condition, 85 fair, and 7 poor (3.6%). “Poor” means a main part — the deck, the beams, or the supports — is rated 4 or lower on the federal 0–9 scale. It doesn't mean unsafe to drive; unsafe bridges are closed.
| Ferguson Rd. over Little Rock Creek · built 1968 | 430 vehicles a day |
| 62nd over Muddy Creek · built 1991 | 50 vehicles a day |
| McCall Rd over Slough Creek · built 1923 | 35 vehicles a day |
| Clark Rd. over Muddy Creek · built 1968 | 20 vehicles a day |
| 150th over Little Rock Creek · built 1977 | 15 vehicles a day |
| 206th over trib Delaware River · built 1909 | 5 vehicles a day |
Source: Federal Highway Administration, National Bridge Inventory (2025 submission). Includes state, county and city bridges.
Federal grants paid for $1.7 million of work in Jefferson County in fiscal 2025, about $94 per resident — to the county, cities, schools, hospitals, nonprofits and others.
Source: USAspending.gov, grants by place of performance, fiscal 2025 (Oct. 2024 to Sept. 2025). Search it by county to see each award.
From Grants.gov: posted grants listing county governments as eligible, soonest deadline first; research-only and overseas programs left out; list updated 2026-10-13, refreshed weekly. 62 are open in all. Cities, towns, school districts and nonprofits have their own lists there.
Registration deadlines, early voting and polling places for Kansas are on the federal site vote.gov, which links to the state's official election office.
The budget, property tax rates, audits, local officials and offices for Jefferson County come from the county's own records, which we haven't gathered — not gathered, never hidden. See what a full county site looks like, or ask to have Jefferson County built: brayden.ozark@gmail.com.
More of Kansas: the state government and every county in Kansas.
Nearby counties: Leavenworth County (18 mi) · Atchison County (20 mi) · Douglas County (24 mi) · Shawnee County (24 mi) · Jackson County (25 mi) · Wyandotte County (34 mi).