Dennis Ritchie's Home Page - Several historic technical reports, anecdotes, and stories from one of the fathers of Unix. UNIX Past - Historical summary and timeline. History of the BSD Daemon - Various drawings, pictures, and information on the red devil BSD mascot. Includes some utility sources. Concentrates on the evolution of the file system, the process-control mechanism, and the idea of pipelined commands.
Some attention is paid to social conditions during the development of the system.
The History of UNIX - Brief historical commentary with a graphical Unix family tree. Mailing list and archives. A Brief History - Transcript from a talk given at a 1995 Unisys conference tracing the key people and events in Unix history. Includes a timeline and other references. An authoritative and technical overview of the operating system.