Analyses of selected gaging station records from the Mississippi River and Rio Grande show that variations in discharge of these rivers into the Gulf of Mexico reflect major flood events and regional-scale drought intervals known from the historical record. Variations in Rio Grande discharge show good correlation with El Ni?o/Southern Oscillation (ENSO) events and short-term variability. Mississippi River discharge does not show correlation with ENSO events or short-term variability. However, Mississippi River discharge does appear to respond to long-term changes in ENSO variability and mean climate state. The link between historical hydrologic extremes and discharge of the Rio Grande and Mississippi River into the Gulf of Mexico indicates that shelf and slope sediments of the Gulf of Mexico contain a long-term record of flood and drought intervals of the Southwestern and Central United States.