Harpers posters have been published by more than fifty nature- and conservation-oriented organizations, among them the Monteverde Cloud Forest Preserve (Costa Rica), the Cincinnati Zoo, Byrd Polar Research Center, Hawk Mountain Sanctuary in Pennsylvania, Santa Rosa and San Jacinto Mountains National Monument, the Michigan Audubon Society, the Hamilton County (Ohio) Park District, the Cornell Lab of Ornithology, Florissant Fossil Beds National Monument, the Edge of Appalachia Preserve, and the Wilderness Society. Glacier Bay, Alaska, created for Glacier Bay National Park, was one of ten posters Harper was commissioned to create for the National Park Service.