Primarily correspondence, memoranda, reports, and notes regarding Merrill's professional responsibilities (1888-1918). Also family and personal correspondence (1888-1911). Chronological files (1888 1912) contain correspondence on Newberry affairs, Chicago library activities (e.g., Chicago Library Club, Bibliographical Society of Chicago), classification, ALA issues, the Centre for University Extension, Catholicism, and family matters. After 1911, Merrill maintained a subject file which includes reports, proposals, memoranda, and correspondence regarding Newberry Library business, especially technical services. This file ceases in 1919 when Merrill moved to public services. There is also correspondence regarding ALA periodical cards and Merrill's reminiscences of William Frederick Poole. Correspondents include John Vance Cheney, George Watson Cole, Charles A. Cutter, Charles Martel, Carl B. Roden, Ellen Gates Starr, and George E. Wire.