Obsidian sources found on the Modoc National Forest (California) come from a wide range of different source materials. Archeological sites on the forest range from small lithic scatter and isolates to complex villages and structures. The predominant sources of obsidian extend from the west side of the forest at Medicine Lake and Blue Mountain to the east into the Warner Mountains on the Nevada border. The artifacts and corresponding ages show prehistoric trade patterns in and outside of the present day forest. This paper will address patterns of obsidian distribution seen from recorded sites and corresponding ages based on obsidian hydration of projectile points for a definitive age range.