I measured rates of growth of individual Gunnison's prairie dogs (Cynomys gunnisoni) at three towns in the Moreno Valley, New Mexico; at an established prairie dog town (site 1) prior to a plague (Yersinia pestis) epizootic and at two towns reestablished after the epizootic (sites 2 and 3). Populations declined by >99% during the epizootic. After the epizootic, adults had greater mass, and juveniles grew faster than before. At sites 2 and 3, juveniles had high interyear survival (39%), whereas at site 1, prior to plague, survival of juveniles was 17%. At sites 2 and 3, yearlings bred, whereas they did not at site 1. Mean litter size near the end of lactation was 1.5 at site 1 and 5.0 at sites 2 and 3. Application of observed demographic parameters to Leslie-matrix analysis indicated that projected size of population was declining (λ = 0.829) at site 1 and was tripling annually (λ = 2.905) at sites 2 and 3. The difference in λ was mostly due to increased survivorship of juveniles and reproduction at an earlier age in the new towns.