The seafloor off greater Los Angeles, California, has been extensively studied for the past century. Terrain analysis of recently compiled multibeam bathymetry reveals the detailed seafloor morphology along the Los Angeles Margin and San Pedro Basin. The terrain analysis uses the multibeam bathymetry to calculate two seafloor indices, a seafloor slope, and a Topographic Position Index. The derived grids along with depth are analyzed in a hierarchical, decision-tree classification to delineate six seafloor provinces-high-relief shelf, low-relief shelf, steep-basin slope, gentle-basin slope, gullies and canyons, and basins. Rock outcrops protrude in places above the generally smooth continental shelf. Gullies incise the steep-basin slopes, and some submarine canyons extend from the coastline to the basin floor. San Pedro Basin is separated from the Santa Monica Basin to the north by a ridge consisting of the Redondo Knoll and the Redondo Submarine Canyon delta. An 865-m-deep sill separates the two basins. Water depths of San Pedro Basin are ??100 m deeper than those in the San Diego Trough to the south, and three passes breach a ridge that separates the San Pedro Basin from the San Diego Trough. Information gained from this study can be used as base maps for such future studies as tectonic reconstructions, identifying sedimentary processes, tracking pollution transport, and defining benthic habitats. ?? 2009 The Geological Society of America.