Six new Allomyia species from the western United States are described: Allomyia kondratieffi sp. nov., Allomyia leei sp. nov., Allomyia meachamensis sp. nov., Allomyia sarahae sp. nov., Allomyia sheldoni sp. nov., Allomyia whatcomensis sp. nov. The majority of these species were collected from small headwater, high altitude streams on relatively isolated mountain ranges. These species bring the number of known North American Allomyia to 18. Additional notes on state/county distribution records, taxonomic problems, species diagnostics and adult emergence periods for the 18 North American species are provided.