Chem 91 is a legendary, clone-only cultivar that serves as a foundational pillar of modern cannabis genetics. First circulated in the early 1990s, this cultivar is widely credited as the progenitor of the Chemdawg, Sour Diesel, and many OG Kush-derived lines. Its exact genetic origin remains undocumented, contributing to its mystique, but its influence is unmistakable across fuel-forward, high-potency cultivars.