Studies of the oceanic and near-shore distributions of Pacific salmon, whose migrations typically span thousands of kilometers, have become increasingly valuable in the presence of climate change, increasing hatchery production, and potentially high rates of bycatch in offshore fisheries. Genetics data offer considerable insights into both the migratory routes as well as the evolutionary histories of the species. However, these types of studies require extensive datasets from spawning populations originating from across the species? range. Single nucleotide polymorphisms (SNPs) have been particularly amenable for multi-national applications because they are easily shared, require little inter-laboratory standardization, and can be assayed through increasingly efficient technologies. Here we discuss the development of a dataset for 114 populations of chum salmon through a collaboration among North American and Asian researchers, termed PacSNP. PacSNP is focused on developing the database and applying it to problems of international interest. A dataset spanning the entire range of species provides a unique opportunity to examine patterns of variability, and we review issues associated with SNP development. We found evidence of ascertainment bias within the dataset, variable linkage relationships between SNPs associated with ancestral groupings, and outlier loci with alleles associated with latitude.