The Computer History Museum dates the creation of Unix to 1969, when Ken Thompson and Dennis Ritchie built the first version at Bell Telephone Laboratories. The work began not on a powerful new computer but on a small, spare DEC PDP-7 that Thompson pressed into service for the experiment.
That first system was deliberately modest. It had no grand institutional mandate behind it; the 1974 Communications of the ACM paper by Ritchie and Thompson later explained that the system grew from the authors’ wish for a pleasant environment in which to program, rather than from a plan to build an industry standard.
From this small beginning, Unix grew quickly. Within a few years it had moved to the larger PDP-11 line, gained a hierarchical file system and a command interpreter, and attracted a growing group of users inside Bell Labs.
The 1969 PDP-7 work matters because almost every modern Unix-like system, including Linux, the BSDs, and macOS, descends from this single experimental program. An operating system that started on a discarded minicomputer became one of the most copied designs in computing.