The Antarctic Treaty was signed on:

The Antarctic Treaty was signed in Washington on 1 December 1959 by the twelve countries whose scientists had been active in and around Antarctica during the International Geophysical Year (IGY) of 1957-58. It entered into force in 1961 and has since been acceded to by many other nations. The total number of Parties to the Treaty is now 54. Among the signatories of the Treaty were seven countries – Argentina, Australia, Chile, France, New Zealand, Norway, and the United Kingdom.