Stratified glacial deposits in major valleys or lowlands constitute important aquifers in the Northeastern United States. In many locations, stratified drift can be divided into a series of morphosequences, which represent successive time intervals during deglaciation. Deposits are more heterogeneous proximal to the ice contact that at the distal end of the sequence. Coarse-grained sand and gravel deposits, which are usually productive aquifers, tend to be more abundant in the southern part of the glaciated Northeast than farther north. The glaciated region of the Northeastern United States can be classified into several broad hydrophysiographic regions that have distinctive aquifer properties.