Montana is the fourth largest state in the United States. It includes portions of the Northern Great Plains and the Rocky Mountains. The vegetation of Montana is diverse, due primarily to the size of the state and its great topographic relief, which provide strong variation in environmental factors. Montana has a relatively large flora for a northern continental region due to being at the intersection of the Cordilleran, Great Plains and Boreal floristic provinces. This book is a comprehensive field guide to the more than 2,500 species of Montana s vascular plants. It contains descriptions as well as habitat and distribution information based on specimens housed at the state s two major herbaria. Portraits or illustrations of diagnostic structures are provided for nearly one-third of the species.