Techrights.org has a wiki page with a time line of key events in the history of software freedom. It starts from the ratification of the Berne Convention in 1887, which creates mandatory copyright for all works in signatory nations, and runs through to 2020 and the fallout from the coup attempt against RMS:
http://techrights.org/wiki/Free_Software_timeline [techrights.org]
Drawing on the collective experience and knowledge of the community here, what needs clarification, correction, or addition?