
The longest river in the United States isn't the Mississippi River--that's the Missouri. But, the Missouri is part of the huge Mississippi River system that's truly a natural wonder! It contains 250 tributaries in all. Readers learn even more fun facts about the Mississippi River...

The longest river in the United States isn't the Mississippi River--that's the Missouri. But, the Missouri is part of the huge Mississippi River system that's truly a natural wonder! It contains 250 tributaries in all. Readers learn even more fun facts about the Mississippi River...