This study is a taxonomic monograph of the Phacelia Crenulatae group for North America and recognizes thirty-three species and six varieties. A brief discussion of the history, general morphology, phylogeny and cytology is given. All entities are separated by a comprehensive key, followed by a list of types, synonyms, descriptions and general habitat. Distribution maps and illustrations are included. The body of this work is based on herbarium specimens and extensive field observations and collections made throughout much of western North America. These studies have resulted in the description of five new species and several nomenclatural changes.