This part of DS 781 presents data for the depth-to-transition (the depth to the bedrock at the Last Glacial Maximum) map of the Santa Barbara Channel, California, region. The raster data file is included in "DepthToTransition_SantaBarbaraChannel.zip," which is accessible from https://pubs.usgs.gov/ds/781/SantaBarbaraChannel/data_catalog_SantaBarbaraChannel.html. As part of the USGS's California Seafloor Mapping Project, a 50-m-resolution grid of depth to the transgressive surface of the Last Glacial Maximum within California State Waters between Refugio Beach and the Hueneme Canyon and vicinity map area was generated from seismic-reflection data collected in 2007 and 2008 (USGS activities Z-3-07-SC and S-7-08-SC), supplemented with outcrop and geologic structure data from DS 781. The resulting sediment-thickness grid was subtracted from regional bathymetry to determine the depth to the last glacial maximum transitional surface. The resulting grid covers an area of approximately 600 sq km. Contours at 5-meter intervals were derived from this depth-to-transition grid and are also available in this data release.