Conversation so far:
what is the only country that is not a member of the african union?
Morocco withdrew from the AU’s predecessor, the Organisation of African Union, in 1984. Morocco rejoined the Africa Union in January 2017, 32 years after leaving the union's predecessor, the OAU.
what was the reason for Morocco leaving the African Union in 1984?
Morocco, which claims sovereignty over the SADR's territory, withdrew from the Organisation of African Unity, the AU's predecessor, in 1984 due to the admission of the SADR as a member.

Question: when was the union's predecessor founded?
Self-contained rewrite: when was the African union's predecessor, The Organization of African Unity, founded?