1920 - Paris (France) - Mask improvisation at the Ecole du Vieux-Colombier.
1951 - Milan (Italy) - Jacques Lecoq creates the Theatre School of the Piccolo Teatro.
1959 - Opole (Poland) - Jerzy Grotowski founds the Laboratory Theatre.
1963 - (US) - Viola Spolin's Improvisation for the Theater is published.
1975 - New York State (US) - Jonathan Fox develops Playback Theatre.
1977 - Quebec (Canada) - Robert Gravel's Ligue Nationale d'Improvisation stages the first public performance mixing improvisation with sport.
1978 - Calgary (Canada) - Keith Johnstone's TheatreSports first public match.
1978 - Ottawa (Canada) - Carleton High School's Improv Olympics is founded.
1979 - (Canada) - Impro: Improvisation and the Theatre by Keith Johnstone is published.
Main source (with several additions): The Novelty of Improvisation: Towards a Genre of Embodied Spontaneity (open access) by David Alfred Charles - PhD Dissertation - Department of Theatre - Louisiana State University, August 2003. All rights reserved.