Wandering around Portsmouth, New Hampshire in 1892 may be impossible unless a time machine is finally invented; until then, there is this remarkable digital collection from Dartmouth College. As part of their Dartmouth Digital Library Initiatives, this collection brings together Sanborn Fire Insurance maps from the Granite State's many towns and cities. The maps date from the 1880s to the 1940s and they provide excellent documentation of the built environment in these towns and cities during this time. Visitors can zoom in on the maps to look at building footprints, infrastructure improvements, road widths, and so on. The site also contains a link to an online checklist of maps created by the Sanborn Map Company and bibliographic records of books that use these maps as key primary documents in historical research.