Two new species are described from vouchers collected as part of an intensive lichen inventory of Fox Hills Sandstone outcrops in an open space preserve within the city limits of Boulder, Colorado. Candelariella clarkii is characterized by its cryptolecanorine apothecia, chartreuse areolate thallus, and 8-spored asci. Lecidea hoganii is a member of the L. auriculata morphological group characterized by a thick white chalky thallus, pink pigments in the hymenium, and absence of secondary compounds. We provide IUCN conservation assessments for both new species, which should be considered critically endangered. The discovery of two species new to science in a relatively densely populated region of North America illustrates the ecological relevance of small of patches of native habitat, which are certain to become even more important in the future.