These data represent the Substrate Component (SC) of the Coastal and marine Ecological Classification Standard (CMECS) out to -200 m or state waters (PMEP’s boundary) of the West Coast of the contiguous United States. The SC is organized into a branched hierarchy of five nested levels: origin, class, subclass, group, and subgroup. Groups and subgroups of the SC are determined by the dominant substrate (defined as the most abundant in terms of percent cover). This is a data compilation; we cross-walked attributes from 62 datasets into CMECS SC ecological units. These classifications were applied to Nearshore Zones currently part of the Pacific Marine and Estuarine Fish Habitat Partnership’s (PMEP) spatial data system, within the “West Coast USA Nearshore Zones” (PMEP) layer. For full documentation of CMECS, see https://coast.noaa.gov/data/digitalcoast/pdf/cmecs.pdf.