Sampling Purpose: The U.S. Geological Survey collected sediment samples, in 1991-1992, from 25 of the 29 navigation pools on the Upper Mississippi River (UMR). Composite sediment grab and core samples were collected from the lower one-third of each pool. Samples were analyzed for total, organic, and carbonate carbon, total nitrogen, particle size, metals, polynuclear aromatic hydrocarbons, organochlorines, polychlorinated biphenyls, herbicides, fungicides, and sterols. Because each sample represents a large spatial area, the coordinates (UTM) for the first sample, collected along the first transect, were entered into the database to provide positional information.