An examination of data from two continuous stage and discharge streamgages and one continuous stage-only gage on the Middle Mississippi River was made to determine stagedischarge relation changes through time and to investigate cause-and-effect mechanisms through evaluation of hydraulic geometry, channel elevation and water-surface elevation data. Data from discrete, direct measurements at the streamgages at St. Louis, Missouri, and Chester, Illinois, during the period of operation by the U.S. Geological Survey from 1933 to 2008 were examined for changes with time.