Model UN began as a series of student-led Model League of
Nations simulations. The first simulations were called an “International
Assembly”, the first of which was held at Oxford University in 1921. The
President of the first Oxford International Assembly, Mir Mahmood, travelled
to Harvard in 1922. During his trip he urged support for the League of Nations,
and, seemingly inspired the Harvard Liberal Club to create the first American
International Assembly held at Harvard University in 1923.  The International
Assemblies were similar to MUN as participants represented countries, debated
to find resolutions and supported the idea of dealing with international disputes
around a negotiating table; still an uncommon idea at the time. After the Second
World War Model League of Nations transitioned to Model United Nations
after the formation of the Leagues successor organization, the United Nations,
in 1945.   Today, some Model United Nations conferences include simulations
of the League of Nations among their committee offerings.
The first recorded instance of a Model United Nations conference was
at Swarthmore College on April 5, 1947. Over 150 students from over 41
colleges were reported as participating. The delegates simulated a General
Assembly and recommended that member states "establish an international
control and development of atomic energy","conclude a treaty on
disarmament", that the UN adopt "a uniform system for citizenship of refugees",
that the UN amend "the charter to adopt a definition of aggression", and that
nations"promote the reconstruction of devastated areas through economic
assistance through the U.N."