The natural areas in the National Park System offer a fascinating variety -- lush forests, underwater nature trails along coral reefs, deserts in bloom, rivers through patches of wilderness, ever-shifting Atlantic barrier islands. They are precious habitat for wild creatures and vegetation, often serving as the last refuge against encroachment by civilization. Other parks tell about people: the ways of life, important events, and famous individuals from the time when humans first crosses from Asia into N. America some 13,000 years ago up to the present. This guide lists by state more than 170 lesser-known national parks, their accommodations, locations, and historical significance. Photos and maps.