From grizzly bears of Katmai National Park in Alaska to rattlesnakes of Montezuma's Castle in Arizona, take a walk on the wildest side of America's National Parks. By land, sea and sky, this fascinating program crisscrosses parklands to get up close to creatures of all shapes and sizes, including the pronghorn, one of the fastest land mammals. Dedicated national park workers also reveal what it takes to nurture generation after generation of these magnificent creatures.