The former British Consulate General, the predecessor of the museum, was the site where the Treaty of Peace and Amity between Japan and the United States was signed in 1854. The museum houses a collection of valuable historical materials related to the opening of Japan to the world and the opening of Yokohama Port. It is said that Commodore Perry and the shogunate met under the "Tamagusu tree" that still stands in the courtyard. The mascot character "Tanemaru," created in 2009 to commemorate the 150th anniversary of the port's opening, was designed as the "spirit of this Tamagusu tree." Adjacent to the museum is the Port Opening Square, which also displays Japan's oldest brick manhole and sewer pipes.
