It is a varied collection of nearly 4,000 pieces consisting of manuscripts, correspondence, photographs, astronomical working papers, logbooks, a scrapbook reprints, and other miscellaneous printed matter. Hubble's papers reflect both his scientific as well as his public interests. The inclusion of Grace Hubble's correspondence, journals, and memoirs also illuminate Hubble's private life. The first eight boxes of the collection are devoted to manuscripts by Hubble and others. The majority of Hubble's own manuscripts deal with scientific subjects. Edwin and Grace's correspondence takes up the next twelve boxes in the collection. Unfortunately, only a few letters survive from the 1920s and 1930s, but there are significant ones to and from Harlow Shapley, Vesto Melvin Slipher, Willlem de Sitter, Henry Norris Russell, Arthur Stanley Eddington, Joel Stebbins, and Otto Struve. There is alos an important run of correspondence with Nicholas Ulrich Mayall from the 1930s regarding the survey of galaxies they made. There are also five boxes of Hubble's working papers from the period 1925 to 1939. In this group is almost complete documentation for his three papers on cepheid variables (1925-1929), for his 1930 paper entitled The Distribution of Luminosity in Elliptical Nebulae, and for his 1934 papers entitled The Distribution of Extra-Galactic Nebulae.