Background and aims. With the goal of assessing population structure and geographic distribution of haplotype lineages among Lampropeltis elapsoides, we sequenced the ND4 mitochondrial DNA locus from 96 specimens of this snake across its area of distribution. Materials and methods. We relied heavily on formalin-fixed museum specimens to accomplish this analysis. Results. The sequence alignment consisted of 491 bp of the selected gene, with 28% missing data. A simulation used to assess the effect of missing data on population genetic and phylogenetic resolution indicated increased character conflict, but with minimal loss of phylogenetic structure. Conclusion. This limited dataset suggests that L. elapsoides constitutes a largely unstructured population, with both widespread haplotypes and large number of private haplotypes, a moderate level of nucleotide diversity, and a low, but significant, degree of north--south population differentiation. Haplotype structure and frequency, nucleotide frequency, and values for Tajima's D and Fu's F-S indicate a recent range or population expansion following a historic bottleneck.