Nontyphoidal Salmonella arc among the leading causes of food-borne disease in the United States. The aim of this study was to compare nontyphoidal Salmonella spatially and temporally in pig production and design a source tracking tool for Salmonella shedding on farm and contamination at slaughter. In this study, a total of265 nontyphoidal Salmonella spp. were isolated from 20 Iowa herds which were enrolled by cooperative agreement and visited from September 2006 to February 2009. Eleven of the 20 herds had multiple visits. At each farm visit, 30 individual fecal samples were collected. At slaughter, 30 mesenteric lymph nodes were collected. Samples were tested for Salmonella spp. using conventional microbiological methods and serotyped at the National Veterinary Services Laboratory (NVSL). All the 265 Salmonella isolates were further characterized by multilocus sequence typing (MLST).