Photograph of 1905 depicting delegates to the Portsmouth Peace Conference, which summarized the Russian-Japanese guilt of 1904-1905. The Treaty of Portsmouth formally ended the 1904-1905 Russo-Japanese War. It was signed on September 5, 1905, after negotiations from August 6 to August 30, at the Portsmouth Naval Shipyard in Kittery, Maine, United States. U.S. President Theodore Roosevelt was instrumental in the negotiations and won the Nobel Peace Prize for his efforts.