Seven deltaic depositional environments are recognized in the Middle Devonian Hamilton Group in southeastern New York. These are: subaerial delta-plain, beach, channel-mouth bar, outer delta-platform, interdistributary bay, delta-slope, and prodelta. These environments record the onset of delatic conditions in the Middle Devonian and the transition from relatively deeper, offshore environments to shallow nearshore and nonmarine depositional environments. The Hamilton delta prograded onto a shallow shelf in the Appalachian Basin in the absence of subsidence of the basement due to faulting. Wave and current action were important in modifying the growth and shape of the accumulating deltaic pile. The Hamilton deltaic framework appears to be similar to that of the Holocene delta of the Niger River of Africa.