We live-trapped small mammals at 12 sites and compiled data from 3 previous live-trapping studies to document the distribution of the eastern chipmunk (Tamias striatus) in the Shawnee National Forest (SNF) in southern Illinois. Chipmunks were not captured at sites in large areas of the eastern SNF. We collected data on canopy composition and coarse woody debris (CWD) at 8 sites where chipmunks were absent and 5 sites where they were present. Canopy composition and CWD did not differ significantly between sites with and without chipmunks. We could not recognize any geographic barriers that would prevent dispersal into the eastern SNF by chipmunks. Thus, the absence of chipmunks in the eastern SNF seems inexplicable at this time.