Ivan Sutherland's pioneering PhD thesis. Sutherland's data organization in Sketchpad led to OOP, with "objects" and "object instances" as its geometric data structures.
Research began in 1969, intended as an educational environment at Xerox PARC. The Alto was later a graphical programming environment.
First WIMP-like GUI
The first was in 1974 (Bravo), but Gypsy was the first MS Word-like editor in 1975. Both ran on the Xerox Alto
Date is approximate. Developed on the Alta, seems to have had a lot of features of C, but higher-level (threads, exceptions). Gave birth to the later Cedar, a superset with garbage collection. Java lists Mesa as a predecessor.
Released to some "peer-review" folks (universities, corporations), pushed the "everything is an object" paradigm.
Very expensive GUI workstation from Xerox. Implemented in Mesa.
...producing X Windows, Kerberos, precursor of LDAP, etc.
First commercially successful GUI
The Open Software Foundation (OSF) formed to oppose OPENLOOK (from competitors).