Trenton and sub-Trenton rocks of the outcrop regions in New York, Pennsylvania, and Maryland are described, and their conditions of origin and paleogeography are discussed. The basement rocks are considered with respect to regional characters, possible causes of magnetic and isostatic anomalies, and relation to deformation of the Paleozoic sediments. New stratigraphic charts, and new isopachous and paleogeographic maps are presented for the Glenarm, the Lower Cambrian, the Middle and Upper Cambrian, the Lower Ordovician, and the Middle Ordovician sediments of the region, with accompanying discussions of the stratigraphy, regional relations, and sedimentation of the deposits. Brief consideration is given to relations of the Trenton and sub-Trenton at the outcrop in New Yor , Pennsylvania, and Maryland, with respect to search for oil and gas in the more westerly subsurface areas of these sediments.