Flowering vine or weed
This looks like either climbing false buckwheat (Fallopia scandens) or black bindweed (Fallopia convolvulus). They are both in the buckwheat family and there are subtle differences between the two species (in the flowers and seeds). At least four species of Fallopia are known to be present in Maryland. https://www.marylandbiodiversity.com/viewChecklist.php?genus=Fallopia
This article is from Illinois but it provides good information.