Mississippi and Ohio Rivers at Cairo, Ill. map

A 1944 map showing the junction of the Mississippi and Ohio Rivers at Cairo, Ill., used aerial photos and soil borings to produce a color-coded guide to the historic twists and turns of the Mississippi. It is still used today.

Credit: Harold N. Fisk/Mississippi River Commission and the War Dept.

http://www.nytimes.com/slideshow/2011/05/08/weekinreview/08flood-slide-show.html
http://www.nytimes.com/2011/05/08/weekinreview/08mississippi.html