Correspondence; published materials; autobiographical materials; manuscripts; diaries; scientific and non-scientific notes; newspapers and magazine clippings; pictorial materials. The collection concerns Mendenhall's activities and interests in physics, seismology, geodesy, metrology standards, Shakespeare, his theory of composition curves, and numerous professional and scholarly societies such as the American Geographical Society, the National Academy of Sciences, the American Physical Society, the American Antiquarian Society, the Philosophical Society of Washington, and the Franklin Institute. The collection consists mostly of correspondence (1871-1924). The general correspondence of Thomas C. Mendenhall (1892-1896) is concerned with Mendenhall's service with the Coast and Geodetic Survey, Worcester Polytechnic Institute, and Ohio State University, detailing especially his work on the adoption of electrical and metrical standards and the history and growth of Ohio State University. Also included is family correspondence which includes that of his son, Charles E. Mendenhall (1907-1935) consisting mostly of letters written to him by friends and colleagues upon the death of his father, as well as some material to T.C. Mendenhall's estate. Autobiographical materials include a holographic manuscript, "Autobiographical Notes," which span the Mendenhall family history and his life through 1894; also included are annual diaries (1891-1924). The balance of the collection consists of notes, manuscripts, clippings souvenirs and miscellaneous materials concerning Mendenhall's scientific interests and such non-scientific concerns as Ohio (the state), Japan, and Shakespeare.

An addition included materials relating to Mendenhall's time spent in Japan, teaching physics. This includes photographs of friends and physicists in Japan, scenery including the Mendenhall Glacier, instruments, as well as a diary from 1851-1853 with drawings, postcards, and a photo album from Japan.