Take a virtual visit to the Mississippi River Museum. Click on "Features and Exhibits" and then "National Rivers Hall of Fame" to read short biographies of people associated with the Mississippi River.
This page by the Upper Midwest Environmental Sciences Center of the United States Geological Survey has an abundant amount of information on the Mississippi River. Use the "Science Programs", "Maps, Tools, Databases", "Products and Publications", and "Outreach and Education" drop-down menus to access various types of resources. Most of the information is at a higher level of reading, however, there are a number of graphs and pictures that may be useful.