The Open Door policy in China was a diplomatic principle introduced by the United States in 1899, aimed at ensuring equal trading rights for all nations and maintaining China's territorial integrity. This policy was a response to the increasing spheres of influence established by foreign powers in China, and it sought to prevent any one nation from monopolizing trade with the Chinese market. By advocating for open access, the U.S. aimed to promote its economic interests while also supporting China's sovereignty amid imperialist pressures.