It includes the cities of Janesville, Beloit, Edgerton, Evansville, Milton, and Whitewater.

[2] Mark Spreitzer is the senator representing the 15th district since January 2023.

[3] Each Wisconsin State Senate district is composed of three Wisconsin State Assembly districts.

The portion of the district in Jefferson County falls within Wisconsin's 5th congressional district, which is represented by U.S. Representative Scott L. Fitzgerald; the portion in Walworth County and the cities of Janesville and Milton and the eastern part of Rock County fall within Wisconsin's 1st congressional district, which is represented by U.S. Representative Bryan Steil; the remainder of the district, in the western half of Rock county, falls within Wisconsin's 2nd congressional district, which is represented by U.S. Representative Mark Pocan.

Previous politicians of a specific numbered district have represented a completely different geographic area, due to redistricting.