Golden mice (Ochrotomys nuttalli) occur throughout the southeastern United States, and are on the periphery of their geographic range in southern Illinois, where they are a state-listed threatened species. We assessed relative abundance and distribution of populations of golden mice in southern Illinois by mark–recapture and occupancy models, and throughout the core geographic distribution to determine if they should be removed from threatened status (delisted). We also tested the “abundant-center” hypothesis that states that occurrence and abundance of a species is greater in the core of the range than at the periphery. We captured golden mice in 21 of 24 sites in southern Illinois, but only 13 of 24 sites in the core of the range. The total number of individual golden mice captured in southern Illinois (n = 99) was 3.3 times greater (χ²₁ = 36.91, P < 0.001) than in the core (n = 30). Habitat factors at sites (mean number of climbing vines, woody stems, and herbaceous stems) affected occupancy of golden mice; no model variables affected occupancy of sympatric Peromyscus. Based on occupancy models, the probability of capturing golden mice was not affected by occurrence of the potential interspecific competitors white-footed mice (Peromyscus leucopus) or cotton mice (P. gossypinus). Our results for occurrence and abundance of golden mice at the periphery of their range in Illinois do not support the abundant-center hypothesis.