Late/Terminal Archaic (4500-2500 B.P.) modes of broad-bladed biface transmission across Northeastern North America are still rather poorly understood. This present study attempts to test a series of diffusion- and migration-based theories against archaeological data collected from six major river drainages across the Atlantic seaboard, including the Savannah, James, Susquehanna, Delaware, Connecticut, and Penobscot. Preliminary results indicate that Late/Terminal Archaic territorial boundaries were relatively fluid and porous, which is indicative of a highly mobile frontier, and that the modes of broad-bladed biface transmission were complex and multifaceted. Although low level migration and short-distance movements likely occurred, current data, however, indicate that the majority of transmission was by way of diffusion-based processes, better typified by the movement of ideas, concepts, and material culture, rather than the mass movement of human populations across the Atlantic seaboard.