The sterile sorediate crustose lichen Bacidina caligans occurs on concrete near Corvallis, Oregon, U.S.A, and is new to North America. Although morpho-chemical identification was unsuccessful, an ITS sequence provided a ready match to a number of sequences of Bacidina adastra and B. caligans in Genbank. Bacidina adastra is thought to occur on eutrophic bark, wood, soil, and rock in Europe, while B. caligans is reported from calcareous rock and concrete. Because B. caligans is a rather cryptic species with few distinctive features that are reliably present (apothecia and pycnidia are typically absent), it is almost certainly more widespread and abundant in Pacific coastal states of North America than this single record would suggest. In addition to the long conidia, other notable features include a green thallus that turns a drab tan after only a month or two indoors, green soralia that coalesce into a continuous leprose thallus, and spot tests that are negative for K, KC, C, and P. Keywords: Bacidina adastra, lichenized fungi, Ramalinaceae, sterile sorediate crustose lichens, eutrophic lichens, concrete.