This biogeographic assessment represents the continuation of an ongoing partnership between the National Marine Sanctuary Program (NMSP) and the National Centers for Coastal Ocean Science (NCCOS). The purpose of this collaboration is to provide sanctuary managers with basic information on the distribution of marine flora and fauna relevant to the national marine sanctuaries they manage. This particular work, conducted in collaboration with the Channel Islands National Marine Sanctuary (CINMS) and members of the local research community, builds on a previous assessment developed for California’s other three national marine sanctuaries (NOAA, 2003). These efforts were undertaken specifically to support the management plan revision process mandated for each sanctuary. This process evaluates the degree that each sanctuary is meeting its goals and allows an opportunity for the public to determine if there are new directions or issues that they feel the sanctuary should address. One issue raised by the public during the CINMS management plan revision process was whether the sanctuary boundaries should be expanded. A significant portion of this document, therefore, is devoted toward providing a biogeographic assessment of the differing boundary concepts previously developed by CINMS in conjunction with the Sanctuary Advisory Council and general public. This was accomplished by a thorough analysis of the biogeographic datasets provided to the analytical team by the local research community. Additionally, the data gathered, analyses performed, and patterns of distribution observed should provide invaluable information to support science, education, and support other spatially-explicit management decisions.