During 1933–1946, organic geochemistry coalesced around the fate of biogenic matter through geochemical processes, anchored by a kerogen-centered view of oil genesis and by early quantification of dissolved and particulate organic matter in aquatic systems. Investigations emphasized characterizing soil organic matter and mineral interactions, including lignin structures and metallo-organic complexes, and advanced analytical approaches for tracing carbon, nutrients, and trace elements in water bodies and soils. A unifying methodological pattern emerged: cross-discipline integration of organic chemistry, mineralogy, and biogeochemistry to track organic matter through environmental and geological cycles. Historical Significance: This period established the kerogen-derived framework as foundational to organic geochemistry, linking biology to petroleum formation and to carbon cycling in soils and waters. Pioneering methods for dissolved organic carbon and nitrogen in seawater, and systematic studies of particulate versus dissolved organic matter in lakes, broke new ground in quantifying and conceptualizing organic material in natural systems. The cross-cut of phytoplankton organic phosphorus utilization and soil phosphorus pool characterization further anchored organic matter as a central driver of biogeochemical dynamics, shaping subsequent research on soil–mineral interactions, nutrient cycling, and environmental geochemistry.