dc. the organization of american states oas is the worlds oldest regional organization, dating back to the first international conference of american states, held in washington, d.c., from october 1889 to april 1890. at that meeting the establishment of the international union of american republics was approved. the ter of the oas was signed in bogotá in 1948 entered into force in december 1951. the ter was subsequently amended by the protocol of buenos aires, signed in 1967, which entered into force in february 1970 by the protocol of cartagena de indias, signed in 1985, which entered into force in november 1988 by the protocol of managua, signed in 1993, which entered into force on january 29, 1996 by the protocol of washington, signed in 1992, which entered into force on september 25, 1997. the oas currently has 35 member states. in addition, the organization has granted permanent observer status to 62 states, as well as to the european union. lang=en xmllang=en