In this paper we segregate specimens from the genus Sticta in the Great Smoky Mountains National Park into phenotypic groups corresponding to putative species using traditional taxonomic methods, paying particular attention to specimens from the S. weigelii s. l. group, then employ phylogenetic analyses and rigorous statistics to test the robustness of these species groups. In order to circumscribe putative species and to resolve the S. weigelii complex, morphological, chemical, and molecular characters from the nuclear ribosomal DNA sequences of the entire Internal Transcribed Spacer region are analyzed separately and simultaneously using maximum parsimony or maximum likelihood. In addition to the bootstrap method, Bayesian statistics with the Markov Chain Monte Carlo algorithm are used to estimate branch robustness on the resulting reconstructed trees. Five out of six analyses recover the same five monophyletic putative species from the genus Sticta, indicating the concordance of DNA-based and morphology-based species delimitation. The phylogenies show that lichens identified as S. weigelii represented S. beauvoisii and the two new species described here – S. carolinensis and S. fragilinata. Sticta weigelii s. s. does not occur in the park. Specimens from Oregon identified as S. weigelii belong to another unnamed Sticta taxon. The remaining two monophyletic groups represent two species well known from the park–S. fuliginosa and S. limbata. Characteristics of secondary compounds detected by Thin Layer Chromatography (TLC) and High Performance Liquid Chromatography (HPLC) in S. fragilinata thalli are provided. Detailed descriptions, including morphology and chemistry, are provided for four Sticta species found in the Smoky Mountains: S. beauvoisii, S. carolinensis, S. fragilinata and S. fuliginosa.