The flora of the Washington (D.C.) -Baltimore Area is rich in number and diversity of species. Nearly 2,800 species of native and naturalized vascular plants (ferns and fern allies, conifers and flowering plants) have been catalogued in this region. The region includes mountain, Piedmont, and coastal plain habitats and thus embraces a wide variety of ecological conditions. Local plants have been studied since at least the 1830s ("A Prodromus of the Flora Columbiana"), and the DC Herbarium, located within the U.S. National Herbarium, was established as an integral part of that research. An up-to-date Annotated Checklist of the Vascular Plants of the Washington-Baltimore Area has been completed in two parts (Part I, 2000;Part II, 2002) by Stanwyn Shetler and Sylvia Orli. Plant specimens from the DC area are completely inventoried and can be accessed in the online data catalog.