Jon - Good catch and that is a good reminder.

Warner - You need to add troff and the C/A/T to your timeline.  They were too important.   What I don't remember, although Doug or Steve might, was the original troff 4th or 5th edition?  bwk did ditroff, later with the addition of the APS5.

FWIW: It was for 6th edition and post 1BSD that Tom Ferin did the original vcat(1) work at UCSF's PDP-11.   It would get spread later to the world as part of one of the BSDs, but the original emulation of a C/A/T4 with a plotter support came from Tom, his graphics lab and the earlier work with the Hershey fonts that CMU and Stanford had done to support the XGP for the PDP-10s.  But that was super important for why people wanted UNIX early on.