See http://www.shitshifter.com/cgi-bin/wiki.pl?MountainBiking for a description of mountain biking.
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North Dakota "Mountain" Biking
http://www.ninebelow.com/ndmb/wiki/index.php?title=Main_Page
The Maah Daah Hey trail connects the northern and southern portions of Theodore Roosevelt National Park, and winds through North Dakota's badlands to form the longest continuous singletrack mountain bike trail in America.
Maah Daah Hey Trail
http://www.ninebelow.com/ndmb/wiki/index.php?title=Maah_Daah_Hey