Open Door, maintenance in a certain territory of equal commercial and industrial rights for the nationals of all countries. As a specific policy, it was first advanced by the United States, but it was rooted in the typical most-favored-nation clause of the treaties concluded with China after the Opium War (1839–42). Although the Open Door is generally associated with China, it also received recognition at the Berlin Conference of 1885, which declared that no power could levy preferential duties in the Congo basin.
