A taxonomic treatment of aquatic and wetland vascular plants has been developed as a tool for identifying over 500 plant species inhabiting wetlands of the northern Great Plains region. The treatment provides dichotomous keys and botanical descriptions to facilitate identification of all included taxa. Illustrations are also provided for selected species. Geographical ranges and habitat preferences are described for each species, and a map is provided for each plant showing its documented occurrences by counties within the region. Additional information provided with species descriptions includes common name(s), flowering/fruiting periods, and nomenclatural synonyms. A glossary of botanical terms is also provided.