Phytophthora root and stem rot (PRR) is a major disease affecting soybean crops worldwide. PRR is caused by Phytophthora sojae, a soilborne pathogen that is managed by the deployment of major genes known as Rps (Resistance to Phytophthora sojae). To date, 32 Rps genes have been mapped but not all are effective, or their effectiveness has been evaluated in the US. The PI 424354 was identified as a potential source of novel Rps genes. A recombinant inbred mapping population, PI 424354 x Williams, was advanced to F_5:7 by single seed descent. Seedlings from 81 recombinant inbred lines (RILs) were phenotyped to different pathotypes of P. sojae corresponding to isolates OH1 (vir 7), OH4 (vir 1a, 1c, 7), OH7 (vir 1a, 3a, 3c, 4, 5, 6, 7), and OH25 (vir 1a, 1b, 1c, 1k, 7), and further genotyped using an Illumina Infinium SNP-6K BeadChip array. Single marker association analysis was first done using ANOVA, and significant markers were used to create linkage maps. High-density SNP mapping and single marker association analysis detected two new putative Rps loci on chromosomes 11 and 19, as well as previously reported resistance loci to P. sojae isolates on chromosomes 3, 13 and 18. Five independent Rps genes were mapped in this RIL population PI424354 x Williams, 2 towards OH 7, and 3 towards OH1, OH4, and OH25. This indicates that there are effectors within isolates of P. sojae for additional Rps genes and emphasizes the importance of screening new sources towards a wider range of isolates prior to breeding.