Distributional and habitat data are presented for sixteen taxa of vascular plants from the Appalachian Plateau and Ridge and Valley Provinces of the state of Maryland. Five of these taxa are reported for the first time from Maryland: Helianthus laevigatus, Juncus articulatus, Solidago curtisii, Viola rostrata X V. striata, and the Vittaria gametophyte. Five species currently are listed as rare or endangered in Maryland: Cyperus lancastriensis, Dryopteris campyloptera, Epilobium leptophyllum, Lemna trisulca, and Poa alsodes. Information is provided for four other significant indigenous taxa: Aconitum uncinatum, Carex debilis var. rudgei, Carex digitalis, and Solidago arguta var. harrisii. The occurrence of three non-indigenous species is discussed: Arthraxon hispidus, Microstegium vimineum, and Veronica chamaedrys. Suggestions are made for future revisions of Maryland’s list of rare and endangered species.