[1] Located in southeast Wisconsin, the district comprises the southeast corner of Racine County, including the south side of the city of Racine, most of the village of Mount Pleasant, and the villages of Sturtevant and Elmwood Park.

The district also contains Johnson Wax Headquarters, Regency Mall, and the Foxconn in Wisconsin campus.

[2] The district is represented by Democratic minority leader Greta Neubauer, since January 2018.

Other than the 1982 redistricting, which temporarily scrambled State Assembly districts, the boundaries of the 66th district remained relatively consistent for the next 40 years (1972–2011), comprising most of Kenosha County with a rotating set of rural towns from Racine and Walworth counties.

[6][7] This was done as part of a broader gerrymander of the southeast Wisconsin districts to pack the majority of Racine and Kenosha Democratic votes into one state senate district.