This article offers a reassessment of the sources of archaeological obsidian found in southern California and northern Baja California based on new information regarding the geological availability of obsidian in Baja California, Mexico. In particular, we demonstrate that a previously unknown obsidian chemical group, referred to here as Tinajas obsidian, was for decades misidentified as San Felipe obsidian in regional archaeological analyses. In light of new data derived from geological surveys, geochemical analyses, and regional archaeological research, previous obsidian provenance reports from both sides of the border are reviewed. Our findings indicate that the archaeological distribution of the Tinajas obsidian group extends throughout northern Baja California and into southern California. In contrast, San Felipe obsidian appears to have had a more restricted geographical distribution than previously thought.