The treaty was initially ratified in 1947, with Bahamas as the most recent country to sign and ratify it in 1982. It came into force in 1948 (in accordance with Article 22 of the treaty).
The treaty was adopted by the original signatories on 1947-09-02 in Rio de Janeiro (hence the colloquial name "Rio Treaty"). It came into force on 1948-12-03. It was registered with the United Nations on 1948-12-20. It was the formalisation of the Act of Chapultepec, adopted at the Inter-American Conference on the Problems of War and Peace in 1945 in Mexico City. The United States had maintained a hemispheric defense policy under the Monroe Doctrine, and during the 1930s had been alarmed by Axis overtures toward military cooperation with Latin American governments, in particular apparent strategic threats against the Panama Canal. During the war Washington had been able to secure Allied support from all individual governments except Uruguay, which remained neutral, and wished to make those commitments permanent.
The treaty was invoked numerous times during the 1950s and 1960s, in particular supporting the United States during the Cold War
This was seen by Latin American countries as the final failure of the treaty. In 2001, the United States invoked the Rio Treaty after the September 11 attacks but Latin American democracies did not join the "War on Terror" actively.
In September 2002, citing the Falklands example and anticipating the Iraq War, Mexico formally withdrew from the treaty; after the requisite two years, Mexico ceased to be a signatory in September 2004.