This data set contains Supplemental Official OCS Block Diagram (SOBD) images in Adobe pdf format for areas within the BOEM Alaska Region. Each SOBD describes a single block within an Official Protraction Diagram (OPD) and shows the lines (Submerged Lands Act, Limit of '8(g) Zone', maritime boundaries and/or marine sanctuaries) which occur within that block and divide it into different areas. The SOBD contains additional coordinates and area calculations for an individual block. These data are scanned images of the official paper SOBD's produced by the BOEM. Note that not all OPDs have boundaries cutting through them, so not all OPDs will have SOBDs generated for them. All current leasing activities will be done using the most current SOBDs. Historical (outdated) SOBDs can be obtained by contacting the Geospatial Services Division. Further information on the historic development of OPD's can be found in OCS Report BOEM 99-0006: Boundary Development on the Outer Continental Shelf: https://www.boem.gov/uploadedFiles/BOEM/Oil_and_Gas_Energy_Program/Mapping_and_Data/99-0006.pdf Also see the metadata for each of the individual GIS files used to create these SOBDs. The Official Protraction Diagrams (OPDs) and Supplemental Official Block Diagrams (SOBDs), serve as the legal definition for BOEM offshore boundary coordinates and area descriptions.