Yokohama Port Museum

From the website: 

"Yokohama Port Museum is the first museum featuring the Port of Yokohama. In April 2009, the Museum was totally remodeled from Yokohama Maritime Museum (opened in 1989) by the 150th Anniversary of the Port Opening Commemorative Project. Under the theme of “Port of Yokohama in history and life”, the exhibits focus on the history, operation and role of the Port of Yokohama. The Museum also provides special exhibitions, lectures, tours and craft classes.
There is a permanent installation of work by artist Ryohei Yanagihara, responsible for the famous “Uncle Torys” design used by Suntory."

The museum is open from 10 am to 5 pm. Adult admission is 500 yen for the museum alone, or 800 yen for a combined ticket of the Nippon Maru Ship and the museum. The museum and ship are located five minutes by foot from the Sakuragicho Station. 

I was the only one visiting (that I could see) the museum at the time I was there. The displays looked new and were very interesting, showing the development of the port area. I recommend visiting both the museum and the Nippon Maru Ship.