In our search to document the fruits of Chenopodium L. taxa in North America to assist identifications, and after demonstrating fruits to be stable and diagnostic, we here focus on the some of the “narrow-leaved” group taxa prevalent in the western part of the continent. For this study, we sampled and classified, employing fruit characters as the leading criteria for categorization, more than 500 herbarium collections of Chenopodium of western North America, with a special focus on California. We concentrated only on taxa with fruits with adherent pericarp and lanceolate to lance-ovate, entire, un-lobed, or basally lobed leaves. Here, we recommend the recognition anew of C. incognitum Wahl as a separate species from C. hians Standley and 10 new species of Chenopodium in California and nearby states of western North America. The recognition of these taxa contributes to an ongoing study of the taxonomy of native Chenopodium in California, where an in-depth local taxonomic treatment of the genus has never before been presented. Our classification is supported both by biogeographical distribution and morphological characters. Taxonomic keys are provided.