What perhaps surprising subjects are covered by Serial Set Maps?
Examples include the spread of diseases, both animal and human; evolution of air routes; railroad acquisitions and mergers, including railroad routes; Indian reservations, including migration and border changes; rivers, including development of navigation, exploration, locks and dams and flood control; public land and railroad surveys; Boxer Rebellion; Commodore Perry Exploration of the Orient; Jeannette Expedition; Philippine War; irrigation development in India; weather; Civil War; census information; voting and political districting and many others.