Jefferson County is a county in Wisconsin, United States, on the Rock River in the south-central part of the state. It had a population of 84,900 at the 2020 census and covers 583 square miles (1,510 km2) — 556 square miles (1,440 km2) of land and 26 square miles (67 km2) of water — centred near 43°01′N 88°47′W.
Jefferson is the county seat; its postal code is 53549. The county holds 6 cities, 5 villages and 16 townships, plus a scattering of unincorporated communities, and sits in the Central time zone under FIPS code 55055.
Towns & Villages in Jefferson County
Jefferson County’s 35 named places split into 6 incorporated cities, 5 incorporated villages and roughly two dozen unincorporated communities and lake settlements without their own municipal government. Several straddle a county line and are governed partly by their neighbor: Watertown reaches north into Dodge County, Whitewater reaches south into Walworth County, Cambridge is mostly in Dane County, and Lac La Belle is mostly in Waukesha County. Verified 2020 per-place population figures were not available for this rewrite and are left blank rather than estimated; the county-wide total of 84,900 above is the sourced figure. Type key: City · seat = county seat; CDP/Unincorp. = unincorporated place with no city or village government of its own.
| Place | Type | Township | Pop. | ZIP |
|---|---|---|---|---|
| Jefferson | City · seat | — | — | 53549 |
| Fort Atkinson | City | — | — | 53538 |
| Lake Mills | City | — | — | 53551 |
| Waterloo | City | — | — | 53594 |
| Watertown | City | — | — | 53094 |
| Whitewater | City | — | — | — |
| Cambridge | Village | Oakland (part) | — | — |
| Johnson Creek | Village | Aztalan | — | 53038 |
| Lac La Belle | Village | — | — | — |
| Palmyra | Village | Palmyra | — | 53156 |
| Sullivan | Village | Sullivan | — | 53178 |
| Aztalan | Unincorp. | Aztalan | — | — |
| Blackhawk Island | Unincorp. | Koshkonong | — | — |
| Breezy Knoll | Unincorp. | — | — | — |
| Busseyville | Unincorp. | Watertown | — | — |
| Carcajou | Unincorp. | — | — | — |
| Ebenezer | Unincorp. | — | — | — |
| Glenn Oaks Beach | Unincorp. | Koshkonong | — | — |
| Grellton | Unincorp. | — | — | — |
| Heath Mills | Unincorp. | — | — | — |
| Helenville | Unincorp. | — | — | 53137 |
| Hoopers Mill | Unincorp. | — | — | — |
| Hubbleton | Unincorp. | Milford | — | — |
| Jefferson Junction | Unincorp. | Jefferson | — | — |
| Koshkonong Manor | Unincorp. | Koshkonong | — | — |
| Koshkonong Mounds | Unincorp. | Koshkonong | — | — |
| Kroghville | Unincorp. | — | — | — |
| North Shore | Unincorp. | Koshkonong | — | — |
| Oak Hill | Unincorp. | — | — | — |
| Pipersville | Unincorp. | — | — | — |
| Portland | Unincorp. | — | — | — |
| Rome | Unincorp. | — | — | — |
| Slabtown | Unincorp. | — | — | — |
| Spacious Acres | Unincorp. | Koshkonong | — | — |
| Sylvan Mounds | Unincorp. | — | — | — |
| Vinnie Ha Ha | Unincorp. | Koshkonong | — | — |
Three place names on the county’s rolls describe water, not settlements, and are covered under Geography instead of the table above: Lake Koshkonong, Lake Lac La Belle and Lake Ripley. A fourth old entry, a bare “Milford,” duplicated the Town of Milford already listed in the townships table below and was folded into it.
Townships
| Township | Pop. (2020) | Main settlements |
|---|---|---|
| Watertown | — | Busseyville |
| Koshkonong | — | Blackhawk Island, North Shore, Vinnie Ha Ha |
| Ixonia | — | Lac La Belle |
| Concord | — | — |
| Oakland | — | Cambridge (part) |
| Aztalan | — | Aztalan, Johnson Creek |
| Farmington | — | — |
| Lake Mills | — | — |
| Milford | — | Hubbleton |
| Jefferson | — | Jefferson Junction |
| Hebron | — | — |
| Cold Spring | — | — |
| Sumner | — | — |
| Waterloo | — | — |
| Palmyra | — | — |
| Sullivan | — | — |
Verified 2020 township-level population figures were not available for this rewrite, so the population column is left blank rather than estimated; the totals roll up into the county-wide count of 84,900 above.
ZIP Codes
- 53538 — Fort Atkinson
- 53094 — Watertown
- 53549 — Jefferson (also serves Jefferson Junction)
- 53551 — Lake Mills
- 53594 — Waterloo
- 53038 — Johnson Creek
- 53036 — Ixonia
- 53156 — Palmyra
- 53178 — Sullivan
- 53137 — Helenville
Whitewater, Cambridge and Lac La Belle sit close enough to the county line that their addresses run under post offices based in neighboring counties, so none of the three carries a Jefferson County ZIP code of its own.
Geography
Jefferson County straddles the Rock River, which runs southeast through the county and widens into Lake Koshkonong — at roughly 10,460 acres, one of Wisconsin’s largest inland lakes — along the county’s southern edge near Fort Atkinson and Milton. The Crawfish River drains the northern townships before joining the Rock near Jefferson, and smaller kettle lakes including Lake Ripley (near Cambridge) and Lac La Belle (on the county’s eastern edge toward Waukesha County) sit in the rolling, glacially formed terrain that covers most of the county. Jefferson County borders Dodge County to the north, Waukesha County to the east, Walworth County to the southeast, Rock County to the southwest and Dane County to the west.
Demographics
Jefferson County had a population of 84,900 at the 2020 census, spread across roughly 153 people per square mile of land area. The county’s two largest communities are Watertown, whose city limits are split with Dodge County to the north, and Fort Atkinson, the largest city entirely inside Jefferson County. Median household income in the county runs close to the Wisconsin state median of $74,631, reflecting a mix of manufacturing wages, dairy-farm income and a growing commuter population working toward Madison and Milwaukee.
Economy & Local Life
Agriculture remains a visible part of the county’s economy, with dairy farms and corn and soybean fields covering much of the townships outside the Interstate 94 corridor. Fort Atkinson is home to Jones Dairy Farm, a family-owned meat-packing company founded there in 1889, and to Nasco, a longtime educational-and-farm-supply manufacturer. The village of Waterloo is the headquarters of Trek Bicycle Corporation, one of the world’s larger bicycle manufacturers, and Watertown hosts Maranatha Baptist University. The Jefferson County Fair, held each July at the fairgrounds in the city of Jefferson, is one of Wisconsin’s larger county fairs and draws visitors from across the region.
History
Jefferson County was created by the Wisconsin Territorial Legislature in 1836 and organized as a functioning county government in 1839, taking its name from settlers who had come from Jefferson County, New York. The Aztalan area in the county’s north, on the Crawfish River, holds the ruins of a Mississippian-culture village occupied roughly 1000 to 1300 AD; the site was rediscovered by settlers in the 1830s, gave the Town of Aztalan its name, and is preserved today as Aztalan State Park. Watertown, straddling the county line with Dodge County, grew into a 19th-century milling and manufacturing center on the Rock River, while Fort Atkinson takes its name from a temporary military post built during the 1832 Black Hawk War.
Getting There
Interstate 94 crosses the northern part of the county through Watertown and Johnson Creek, and US Routes 12 and 18 run through Jefferson and Fort Atkinson, along with Wisconsin Highways 16, 19, 26, 59, 89, 106 and 134.
- Madison — about 30 miles west
- Milwaukee — about 45 miles east
- Watertown — about 15 miles north of Jefferson
- Whitewater — about 12 miles south of Fort Atkinson
Dane County Regional Airport in Madison and Milwaukee Mitchell International Airport are the nearest commercial airports, each roughly 30 to 45 miles from the county’s population centers.
Frequently Asked Questions
Where is Jefferson County, Wisconsin?
It sits in south-central Wisconsin along the Rock River, between Madison and Milwaukee, bordered by Dodge, Waukesha, Walworth, Rock and Dane counties.
What is the population of Jefferson County?
84,900 people, at the 2020 census.
How big is Jefferson County?
583 square miles (1,510 km2), of which 556 square miles is land and 26 square miles is water.
What is the county seat of Jefferson County?
The city of Jefferson.
How many towns and villages are in Jefferson County?
6 cities, 5 villages and 16 townships, plus about two dozen unincorporated communities.
What ZIP codes are in Jefferson County?
Ten standard ZIP codes, from 53036 (Ixonia) and 53038 (Johnson Creek) to 53594 (Waterloo) — see the ZIP Codes table above for the full list.
What is Jefferson County known for?
The Aztalan archaeological site, Lake Koshkonong, Trek Bicycle Corporation’s headquarters in Waterloo, and Jones Dairy Farm in Fort Atkinson.
More counties in this state: Towns and villages in Wisconsin.