Exploration of the lichen diversity in southeast Iowa has historically been limited. Prior to this study only 124 of the total 7,644 known specimens of Iowa lichens (1.6%) were from four counties in southeast Iowa. After two years of field work a total of 150 species were identified from 395 specimens, 18 of which are new records for the state. Only 29 of the species found had been previously documented in southeastern Iowa. Integration of these collecting efforts with previous efforts provides an estimate of 465 species of lichens reported for Iowa. Of these species, 33 macrolichen species are likely to be rare in, or extirpated from, the state.