Search by subject, typing the place name and then maps:
ex: United States maps, Massachusetts maps, Boston maps
Other subject terms to try:
map collections, maps and mapping, maps, early, cartography
Maps are often included as plates in books; use a subject search in Barton, then choose the "Full display" option to see whether the book includes maps.
For atlases, use a combined keyword search: subject [place name] and keyword [atlas*]