The authors collected samples of 97 populations of the wild potato S. stoloniferum (previously fendleri) in the following seven mountain ranges of the southwest USA over 7 years, 2004-2010: Chiricahua (CHI), Huachuca (HUA), Rincon (RIN), Guadalupe (GUA), Pinaleno (PIN), Santa Catalina (CAT), and Santa Rita (RIT). These and previous samples were compared with AFLP markers to determine which ranges have the most genetic richness. A total of 2,079 bands were polymorphic over all populations, and 1,256 were polymorphic among ranges. Of these 1,256 bands, 279 occurred in only one range (= unique). All mountain ranges had some unique bands, but not equally, as PIN with 30%, and CHI with 22% together accounted for over 50% of the unique bands in the seven ranges. An examination of populations within ranges showed that one localized area was the source of over 50% of the unique bands from PIN. This study demonstrates that DNA markers can identify collecting locations like PIN and CHI with particular genetic richness, and thus these locations have high priority for further sampling for the genebank. Similarly, these populations already present in the genebank could be prioritized for evaluation and preservation based on the relative number of unique bands they contribute from their range. The discovery of substantial new diversity in each range implies that other ranges not yet fully explored are likely to also contain novel valuable germplasm, and that collecting in the USA is not complete. © 2011 Potato Association of America.