The coastal or Humboldt marten (Martes caurina humboldtensis) is a genetically distinct subspecies of the Pacific Marten that historically occurred throughout the coastal forests of Oregon and California. The known distribution of the Humboldt marten today is limited to four small and isolated populations that together encompass <10% of the historical range. Low abundance and long-term isolation raise the possibility that inbreeding depression threatens population viability in addition to more deterministic threats such as habitat loss and predation. To investigate the extent of inbreeding, we sequenced whole genomes of Humboldt martens from the smallest and most isolated population center in central coastal Oregon. We compared whole-genome heterozygosity, degree of genetic differentiation, and individual levels of inbreeding based on runs of homozygosity to marten genomes from the larger, more continuous population in the Cascades. These preliminary findings offer insight into the historical demographic trajectory of the Humboldt Marten and the likelihood that anthropogenic fragmentation has resulted in reduced fitness.