The Mississippi River has been providing water, transportation, and blues songs to us for hundreds of years. The river was essential in building trade, agriculture, and settlements in the United States. And it continues to be crucial in ways we rarely think about. In combination with the Missouri River, which flows into the Mississippi, it's the fourth longest river on Earth. Learn more about the mighty Missisippi at Environmental Graffiti. Link
(Image credit: Flickr user Michael Hicks)