Photo #25455 - Theodore Roosevelt National Park, North Dakota Large spherical boulders in front are called concretions. Theodore Roosevelt National Park Pick up the trail of America's greatest legends in North Dakota, and you'll find yourself in a legendary adventure of your own. Lewis and Clark, Sakakawea, George Custer, Sitting Bull and Theodore Roosevelt lived out larger-than-life adventures here. Whether you follow in their footsteps and rediscover the past or blaze your own trail and discover what makes North Dakota legendary today, you'll find wide-open spaces and wide-open fun!