On March 31, 1854, U.S. Commodore Matthew Perry and representatives of the Japanese government signed the Convention of Kanagawa. The terms of the treaty marked the end of Japan's 500 years of self-imposed isolation by opening of the Ports of Shimoda and Hakodate. Four years later, Japanese-American relations were further expanded by the Treaty of Amity and Commerce (Harris Treaty), which opened more Japanese ports to U.S. trade and set up a system of extraterritoriality for Americans in Japan.