In 1955 the SHARE volunteer-run user group for IBM mainframe computers was founded in the Los Angeles area by users of the IBM 701, IBM's first commercial stored-program computer. The group evolved into a forum for exchanging technical information about programming languages, operating systems, database systems, and user experiences for enterprise users of IBM computers. Because IBM originally distributed its operating systems in source form, systems programmers commonly made small local additions or modifications and exchanged them with other users. These shared exchanges became the SHARE library, and the process of distributed and collaborative development it fostered was one of the major origins of open source software.
Before the Internet and email SHARE distributions were made by mail, including correspondence, print-outs of programs, decks of punched cards, programs on magnetic tape, etc. The first distribution from SHARE, as documented in the Paul Pierce collection at the Computer History Museum, was issued on October 17, 1955. The group initially paginated its many and long distributions consecutively, apparently giving up this practice when it reached page 13,853 with distribution No. 625 in February, 1959. In 2015 SHARE.org celebrated its 60th anniversary.