Tuesday marked the 99th anniversary of the National Park Service, perhaps the most-loved division of the federal government. For many Americans, excursions to the national parks conjure up memories of family road trips, camp songs and hikes set in some of the country's most beautiful locales. Ken Burns called the parks, "America’s best idea." Cue Woody Guthrie: "This Land Is Your Land." But what's often left unmentioned is that for the parks to become the protected lands of public imagination, their prior inhabitants -- such as indigenous peoples and the rural poor -- had to be evicted.