Exotic populations of Phragmites australis (common reed) are now present in southern New England wetland habitats where native populations were once abundant. We surveyed Rhode Island to determine the distribution of native and exotic P. australis, and used this information to build a publicly accessible Geographic Information System (GIS) database. All P. australis populations sampled on the mainland were exotic. We only found native populations growing throughout a network of tidal marshes and ponds on Block Island, and several of these populations are being overrun by expanding exotic populations. The GIS database from this survey can be expanded to other regions, and can be used for the conservation of the native subspecies and for ensuring that control efforts target only exotic populations.