[2] Jefferson County comprises the Watertown-Fort Atkinson, WI Micropolitan Statistical Area, which is also included in the Milwaukee-Racine-Waukesha, WI Combined Statistical Area.

Jefferson County was created in 1836 as part of Wisconsin Territory and was organized in 1839.

[3] Jefferson County was founded by "Yankee" settlers from New England.

[4] It was named after Jefferson County, New York, where some of the original settlers came from.

As of the census[12] of 2010, there were 83,686 people, 32,117 households, and 21,872 families residing in the county.

23.60% of all households were made up of individuals, and 9.60% had someone living alone who was 65 years of age or older.

There are seven elected officials in addition to the County Board of Supervisors.

Lyndon B. Johnson in 1964 is the last Democratic Party candidate to win a majority of the county's votes.