The 20 most-visited national parks in the U.S.
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17. Badlands National Park( Mark Duncan / Associated Press )
Visitors in 2009 (through August): 776,805
Hundreds of thousands of years of erosion carved Badlands National Park's extraterrestrial-like landscape of multicolored canyons, buttes and spires. Beyond its amazing views, the park contains rich fossil deposits from the Oligocene Epoch dating 28 million to 37 million years ago. Bison, foxes and bighorn sheep roam its prairies.
Faceoff: Mt. Rushmore vs. Crazy Horse Memorial
In South Dakota's Black Hills, echoes of the Old West