There are 72 counties in the U.S. state of Wisconsin. The land that eventually became Wisconsin was transferred from British to American control with the 1783 signing of the Treaty of Paris. It was an unorganized part of the Northwest Territory until 1802 when all of the land from St. Louis north to the Canadian border was organized as St. Clair County. When Illinois was admitted to the union in 1818, Wisconsin became part of the Territory of Michigan and divided into two counties: Brown County in the northeast along Lake Michigan and Crawford County in the southwest along the Mississippi River. Iowa County was formed in 1829 from the Crawford County land south of the Wisconsin River. Brown County's southern portion was used to form Milwaukee County in 1834. The state of Wisconsin was created from Wisconsin Territory on May 29, 1848, with 28 counties. The most populous county in the state is Milwaukee County at 916,205 people at the 2023 Census estimate. The county with the least population is Menominee County with 4,226 residents; the Menominee Indian Reservation is co-extensive with the county. Pepin County is the smallest in area, with 231.98 sqmi; Marathon is the largest, having 1544.91 sqmi. The Federal Information Processing Standard (FIPS) code, which is used by the United States government to uniquely identify states and counties, is provided with each entry. Wisconsin's code is 55, which when combined with any county code would be written as 55XXX. The FIPS code for each county links to census data for that county.

Governance

Each county has a county seat, often a populous or centrally located community, where the county's governmental offices are located. Some of the services provided by the county include: law enforcement, circuit courts, social services, vital records and deed registration, road maintenance, and snow removal. County officials include sheriffs, district attorneys, clerks, treasurers, coroners, surveyors, registers of deeds, and clerks of circuit court; these officers are elected for four-year terms. In most counties, elected coroners have been replaced by appointed medical examiners. State law permits counties to appoint a registered land surveyor in place of electing a surveyor. Counties in Wisconsin are governed by county boards, headed by a chairperson. Counties with a population of 500,000 or more must also have a county executive. Smaller counties may have either a county executive or a county administrator. As of 2011, 13 counties had elected county executives: Brown, Chippewa, Dane, Fond du Lac, Kenosha, Manitowoc, Milwaukee, Outagamie, Portage, Racine, Sawyer, Waukesha, and Winnebago. 23 had an appointed county administrator, 34 had an appointed administrative coordinator, and 2 had neither an executive nor an administrator. Waukesha County had both an executive and an administrator.

List of counties

Renamed counties

Five counties in Wisconsin have been renamed, but otherwise kept their same borders.

Proposed counties

Two proposed counties were ultimately not established.