[1] Located in south-central Wisconsin, the district comprises most of the southern half of Columbia County and part of northern Dane County.

It includes the cities of Columbus and Lodi, and the villages of Arlington, DeForest, Doylestown, Fall River, Poynette, and Rio, as well as part of the north side of the city of Madison including the Greater Sandburg, American Center, Pumpkin Hollow and Truax neighborhoods.

The district also contains Dane County Regional Airport, Madison Area Technical College, and the American Family Insurance corporate headquarters.

[2] The district is represented by Democrat Maureen McCarville, since January 2025.

The 42nd district boundaries have shifted significantly over the various redistrictings of the state, but the location of the district has remained consistent in south-central Wisconsin since the 1983 redistricting.