Boston should be very busy next month hosting leaf peepers there and on their way further north to see the colors. Rooms may be at a premium.
The city is very much about history: Revolutionary War sites on the Freedom Trail and in the suburbs, a Black Heritage Trail, a now-gentrifying Italian neighborhood that has seen changes in the ethnicity of its immigrants over the centuries, traditional brownstone architecture on picturesque Beacon Hill, witch trial history in Salem, traditional seaports nearby, etc. There are many "ethnic" restaurants dotted around the neighborhoods. Lobster is featured on many menus. The city is very much connected to its harbor and the ocean, although by next month it may be a bit cold for many activities. The MFA has some good collections and the Gardner Museum is unique. The PEM in Salem can be reached by train. There is an Aquarium known for its three story central tank, and a science museum. There are pleasant cafés everywhere, including the Italian North End, Harvard Square in Cambridge, Davis Square in Somerville, and wherever there are students (which, because of the number of educational institutions, covers the whole area). It is a pleasant city for walking.

I have to say though that I once drove six hours in the snow with some friends from rural Ohio, and back immediately afterward, simply to spend six hours at the art museum in Chicago--and considered it well worthwhile.