Much about the offshore California Continental Borderland remains unknown, despite its location off the most populated area of the west coast of North America, vital importance to US interests, and potential for seismic and tsunamigenic hazards. In 2015 and 2016, Exploration Vessel (E/V) Nautilus of the Ocean Exploration Trust undertook a series of seven expeditions in that region. During those cruises, we acquired 13,075 km² of multibeam bathymetric data, performed 58 dives with remotely operated vehicles (ROV) Hercules and Argus, totaling 500+ hours underwater (1000+ hours of video), and collected 532 geological and biological samples across this...