Nitrate concentration and flux were estimated from 1980 through 2010 at eight sites in the Mississippi River Basin as part of the National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey (USGS). These estimates extend the results from a previous investigation that provided nitrate estimates from 1980 through 2008 at the same sites. From 1980 through 2010, annual flow-normalized (FN) nitrate concentration and flux in the Iowa and Illinois Rivers decreased by 11 to 15 percent. These two rivers had the high- est FN nitrate concentration in 1980 (5.3 milligrams per liter mg/L] and 3.9 mg/L, respectively) of any of the study sites.