86,245 people (2024 Census estimate, +0.0% since 2020)
556 square miles of land · 155 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.
27 active community water systems list Jefferson County in the area they serve, reporting 61,640 people served in all (a system that crosses county lines counts its whole population).
| WATERTOWN WATERWORKS groundwater · local government · WI1280044 | 23,945 served |
| FORT ATKINSON WATERWORKS groundwater · local government · WI1280103 | 12,390 served |
| JEFFERSON WATERWORKS groundwater · local government · WI1280104 | 7,926 served |
| LAKE MILLS WATERWORKS groundwater · local government · WI1280108 | 6,211 served |
| WATERLOO WATERWORKS groundwater · local government · WI1280115 | 3,520 served |
| JOHNSON CREEK WATERWORKS groundwater · local government · WI1280107 | 3,318 served |
| PALMYRA WATERWORKS groundwater · local government · WI1280112 | 1,756 served |
| AUTUMN RIDGE WATER SYSTEM LLC groundwater · private · WI1281138 | 575 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 115 people were held in Jefferson County's jail, in Vera's latest figure (2024), or 205 per 100,000 residents ages 15–64. In 2019 it was about 193.
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.
8 school districts have their office in Jefferson County. School taxes are usually the largest part of a property tax bill.
Spent $57.6 million — $50.1 million to run schools, about $15,658 per student, plus $799,000 on buildings and equipment. Money in: $21.1 million local (mostly property tax), $36 million state, $6.8 million federal. Long-term debt: $15.4 million.
Spent $48.9 million — $44.3 million to run schools, about $17,539 per student, plus $1.4 million on buildings and equipment. Money in: $23.7 million local (mostly property tax), $26.7 million state, $4.9 million federal. Long-term debt: $4.2 million.
Spent $33.2 million — $27.2 million to run schools, about $15,703 per student, plus $2.4 million on buildings and equipment. Money in: $17.4 million local (mostly property tax), $17.1 million state, $3 million federal. Long-term debt: $24.1 million.
Spent $23.2 million — $20.2 million to run schools, about $13,354 per student, plus $323,000 on buildings and equipment. Money in: $11.8 million local (mostly property tax), $13.5 million state, $2.5 million federal. Long-term debt: $28.7 million.
Spent $16.1 million — $14.2 million to run schools, about $15,523 per student, plus $266,000 on buildings and equipment. Money in: $9.3 million local (mostly property tax), $7.3 million state, $1.3 million federal. Long-term debt: $3.8 million.
Spent $14 million — $11.8 million to run schools, about $15,311 per student, plus $306,000 on buildings and equipment. Money in: $4.7 million local (mostly property tax), $7.9 million state, $1.5 million federal. Long-term debt: $13.8 million.
Spent $13.1 million — $10.4 million to run schools, about $17,174 per student, plus $182,000 on buildings and equipment. Money in: $10.7 million local (mostly property tax), $7.3 million state, $865,000 federal. Long-term debt: $30.2 million.
Spent $15 million — $10.3 million to run schools, about $17,970 per student, plus $492,000 on buildings and equipment. Money in: $7.1 million local (mostly property tax), $6.7 million state, $1.7 million federal. Long-term debt: $8.9 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: Relatively Low compared with other U.S. counties. FEMA estimates natural hazards cost Jefferson County about $41.8 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.
182 bridges in Jefferson County: 101 in good condition, 72 fair, and 9 poor (4.9%). “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.
| CTH N over DEER CREEK · built 1960 | 2,537 vehicles a day |
| CTH D over BARK RIVER · built 1950 | 1,500 vehicles a day |
| LRD ROCK RIVER RD over ROCK RIVER · built 1985 | 185 vehicles a day |
| LRD MORGANS RD over OCONOMOWOC RIVER · built 1951 | 176 vehicles a day |
| LRD WRIGHT RD over JOHNSON CREEK · built 1963 | 155 vehicles a day |
| LRD ROCKDALE RD over KOSHKONONG CREEK · built 1930 | 88 vehicles a day |
Source: Federal Highway Administration, National Bridge Inventory (2025 submission). Includes state, county and city bridges.
Federal grants paid for $21.1 million of work in Jefferson County in fiscal 2025, about $249 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 Wisconsin 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 Wisconsin: the state government and every county in Wisconsin.
Nearby counties: Waukesha County (24 mi) · Walworth County (27 mi) · Rock County (28 mi) · Dodge County (29 mi) · Dane County (33 mi) · Washington County (38 mi).