This vector data set contains the rock unit polygons for the surficial geology in the Delaware Coastal Plain covered by DGS Geologic Map Series No. 26 (Cecilton and Middletown Quadrangles). The geology of the map area reflects a complex history with a cut and fill geometry where the Pleistocene-aged deposits incised into older units. The Tertiary deposits were modified by erosion and deposition of the Columbia Formation during the early Pleistocene and again by the Lynch Heights and Scotts Corners Formations as a result of sea-level fluctuations during the middle to late Pleistocene. The geology is further complicated by periglacial activity that produced Carolina Bay deposits in the map area, which modified the land surface. This map supersedes Geology of the Middletown-Odessa Area, Delaware: Delaware Geological Survey Geologic Map Series No. 2 (Pickett and Spoljaric, 1971).