Recent excavations at two sites located along the coastal margin of the Los Angeles basin revealed three features created as a result of communal mourning ritual during the Intermediate Period (ca. 3000–1000 cal B.P.). Detailed analysis of constituents, structure, and context indicates that formation of these dense concentrations of ground stone implements, unmodified cobbles, other artifacts, and cremated human remains involved deliberate equipment production, sequential implement fragmentation and treatment including burning and pigmentation of items, and secondary interment of incomplete objects and bodies in pits within locales often used for this purpose over many generations. The large size and evident manipulation of objects as part of communal mourning ritual indicates that actions would have been readily visible to a gathered assembly. Thus, while the meaning and significance of these practices remains to be thoroughly explored, the data suggest that communal mourning ritual may have played a significant role in community-building and the maintenance of identity within a region with a dynamic population history.