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Papilio rutulus
kcurtain is correct - Maryland has the Eastern Tiger. Here is a list of the most common butterflies in Maryland for your future reference. :) http://www.thebutterflysite.com/maryland...
Unless the location is wrong on the map, then this is definitely an eastern, not a western, tiger swallowtail. They look almost identical, but the western's range does not extend anywhere near Maryland.