Organized alphabetically by organization or by family name of correspondent. Series also includes attachments and materials sent with correspondence, such as plans, reports, meeting minutes, conference programs, membership directories, and other materials. Correspondents include employees of the companies Spencer ran, coal and mining organizations, biographical companies, institutions with which Spencer had a philanthropic or civic relationship (including the University of Kansas), politicians and members of state and federal governments, and other individuals. Most of the correspondence is business- or professionally-related.