In June 1898, in the midst of the Spanish-American War, the McKinley administration requested that Congress appropriate $20,000 for a commission to study the possibilities of trade with China.  In July, John Hay, then U.S. ambassador to Britain, suggested a joint Anglo-American initiative concerning trade with China, but Secretary of State William Day thought it premature.  In September, a month after a ceasefire in the war, President McKinley mentioned in a speech before the peace commission that his administration felt a duty to expand American trade in China on an equal footing with other nations.  He insisted that the United States wanted not only “an open door for ourselves, [but] … to accord the open door to others.”

With the peace treaty concluding the Spanish-American War signed in December 1898, the way was opened for the McKinley administration to give more attention to China in 1899.  The native rebellion against America’s controversial rule in the Philippines meant that U.S. firepower could not be expended on the Chinese situation without serious military and political repercussions.  Despite improving relations between the United States and Great Britain, lingering animosity in certain American quarters meant that any formal alliance could also hurt the McKinley administration politically.  Therefore, when Tsar Nicholas II of Russia declared on August 11, 1899, that henceforth the Russian-controlled port of Talienwan in Manchuria, China, would be opened to commercial ships of all nations, the McKinley administration determined that the great powers were ready for a unilateral American trade initiative. 

On August 24, 1899, John Hay, who had become secretary of state in September 1898, instructed American diplomat William Rockhill to draft a statement to the Great Powers regarding trade in China.  The president approved the memorandum, which was then sent to Great Britain, France, Germany, and Russia on September 6, and to Italy and Japan soon afterward.  The Open Door policy sought to prevent the powers from restricting trade within their spheres of influence in China and from extending their political authority by carving the country into several colonies. 

The policy articulated three principles:  1) open commercial access to all spheres of influence and treaty ports; 2) the Chinese government alone would be able to collect tariffs and custom duties; and, 3) the Great Powers would have to pay China harbor and railroad fees in their respective spheres of influence.  Initially, Britain agreed in substance with the Open Door note, Russia rejected it, and the other nations were ambivalent; however, by March 1900, Secretary of State Hay had publicly judged all their responses as acceptance of the Open Door policy.