On 27th January 1967, the Outer Space Treaty
(adopted by the UN General Assembly on 19th December 1966)
was opened for signature in London, Moscow and Washington, D.C.
Christopher D. Johnson has published a rather thorough article
(followed by some interesting, thought-provoking comments)
in The Space Review on how this treaty came into being.
Link to: The Space Review, "The Outer Space Treaty at 50"
Link to: Secure World Foundation website