Seismic profiler recordings in 44 profiles between Nova Scotia and the Florida Keys indicate that the continental margin was formed by upbuilding on the shelf and prograding on the slope. Upbuilding on the shelf during the Tertiary and Quaternary Periods ranged from 200 to 1,000 meters, and seaward prograding on the slope during the same span of time was from 5 to more than 35 kilometers. The greatest progradation occurred where the slope is flanked by the Blake Plateau rather than by the deep sea. The beds are truncated along some sections of the slope as though the slope had been steepened by submarine erosion. Off Nova Scotia the beds of the slope continue into the continental rise; off New England the rise consists of sedimentary layers that have buried the base of th continental slope; and off southeastern United States the beds of the Florida-Hatteras Slope have prograded atop the older surface of the Blake Plateau.