From an original membership of 36 states when the OAU was established on 25 May 1963, there have been nineteen successive enlargements—the largest occurring on 18 July 1975 when four states joined. Morocco is the newest member state, having joined in January 2017. Morocco was a founder member of the OAU but withdrew in 1984 following the organization's acceptance of the Sahrawi Arab Democratic Republic as a member state. Morocco rules over most of the territory, but sovereignty is disputed.