The Rock County Historical Society: Your Premier Resource for Historical Research, Thought-Provoking Programs, and Unique Historic Sites. RCHS, in partnership with the City of Janesville, is dedicated to preserving a campus of five historic sites just north of downtown Janesville. These sites highlight the rich history of Janesville and Rock County, Wisconsin. While our tradition centers on preserving history, our mission is to make history engaging and relevant for all residents and visitors.