{Salto Observatory; Sanborn, Vail & Co.; San Diego Business and Professional Women's Club; San Diego County Planning Commission; San Diego Scientific Library; E. Sanger-Sheppherd; W. W. Sargeant; A. P. Saunders; Frederick A. Saunders; George G. Saunders}
{Science Press; Science Progress; Scientia; Scientific American; Scientific International Research Service Corp.; E. M. Scofield; Charles Scribner's Sons; N. P. Scudder; H. von Seeliger; Seismological Society of America; Selznick International Pictures, Inc. [W. E. McCune]; Service; Geneva Seybold; James A. Shanahan; W. N. Shaw; Barbara Sheffield}
{Leo J. Scanlon; William C. Scarritt; Robert O. Schad; Paul W. Schenck; James A. B. Scherer; Frank H. Schleer; Carl Schleicher & Schüll; Hans W. Schneider; Dorothy E. Schoof; J. Schroeter; F. Schuerer; L. Schützenberger; A. Schwassmann}
{Sigma Xi; L. Silberstein; Edward E. Simonds; Frederick Simpich; Arthur W. Sinclair; A. de Sitter; W. T. Skilling; Sarah Louise Slaughenhaup; Paul Slavenas; Frederick Slocum; E. E. Slosson}
{Clem Stoeckle; Julius F. Stone; P. W. Stoner; Clarence Strachauer; Samuel Wesley Stratton; George L. Streeter; Paul Stroobant; Georg Struve; Sunset Press; Sun Yatsen University Observatory; Swarthmore College Library; Eugene Swarzwald; Synchronome Co., Ltd}
{W. M. Smart; Albert M. Smith; Ruth Emily Smith; Sinclair Smith; Smith Premier Typewriter Co.; Smithsonian Institution; Edwin R. Snyder; Sociedad Astronómica de España y América; Società Astronomica Italiana; Société Astronomique de France; Société Francaise de Physique; Society of Writers to H. M. Signet}
{Pacific Electric Railway Co. [incl to/from GEH]; Pacific Geographic Society [Humphrey Read]; Pan American Scientific COngress [José J. Bravo]; Paris Observatory; Const. Parvule; J. Newton Parker; Sir Charles Parsons; Pasadena Association; Pasadena High School and Junior College [Ida E. Hawes]; Pasadena Vocation Bureau [Marion de Paar]; A. W. Pawlow; Fred Pearson; Peckham Bros.; George B. Pegram; Walter M. Pegram; Peking Central Observatory; G. Edward Pendray}
