National parks and reserves 222 Management 152 History 149 Historic sites 112 Planning 102 Antiquities 100 Land use 66 more ... Buildings 49 Buildings, structures, etc 49 Excavations (Archaeology) 47 Indians of North America 44 Historic buildings 41 Environmental aspects 40 Recreation areas 38 Environmental impact analysis 35 Conservation and restoration 31 Archaeological surveying 29 National monuments 26 Trails 26 Homes 23 Homes and haunts 23 Conservation of natural resources 22 Roads 20 Cultural property 19 House furnishings 19 Protection 19 Interpretive programs 18 Historic districts 16 Description and travel 15 Environmental impact statements 15 less ...