In February 2017, a population of California red-legged frog Rana draytonii was discovered in the southern foothills of the San Bernardino Mountains of Riverside County, California, near the edge of the species’ historic distribution. A few days after the first sightings of R. draytonii at the Whitewater Preserve, we conducted a visual daytime search for frogs, tadpoles and egg masses followed by a nighttime eye shine search for adult frogs. The captured frog weighed, measured (snout-to-urostyle [SU]), sampled for tissue and georeferenced using a GPS unit. Survey work was authorized by a U.S. Fish and Wildlife Service Recovery Permit and a California Department of Fish and Wildlife Scientific Collecting Permit. To better understand the origin of these frogs, we extracted DNA from a small toe clip using a Qiagen® DNeasy Kit (Qiagen Inc., Valencia CA) and Sanger-sequenced a region of the cytochrome b mitochondrial gene (986 base-pairs) that has been used to good effect for identifying regionally specific 67 mtDNA clades (Richmond et al. 2014). Sequencing was performed on a 3730xl DNA Analyzer at Genewiz (La Jolla, CA). We used DnaSP 5.10 (Librado & Rozas 2009) to match the haplotype sequence against a large cytochrome B database representing the full range of R. draytonii. These data are associated with the following publciation: Backlin, A., Richmond, J., Gallegos, E., Christensen, C., and Fisher, R. (2017). An extirpated lineage of a threatened frog species resurfaces in southern California. Oryx, 1-5. doi:10.1017/S0030605317001168 These data are associated with the following GenBank accession number: MG022156 References: Richmond, J.Q., Backlin, A.R., Tatarian, P.J., Solvesky, B.G. & Fisher, R.N. (2014) Population declines lead to replicate patterns of internal range structure at the tips of the distribution of the California red-legged frog (Rana draytonii). Biological Conservation, 172, 128-137. Librado, P. & Rozas, J. (2009) DnaSP v5: a software for comprehensive analysis of DNA polymorphism data. Bioinformatics, 25, 1451-1452.