National parks and reserves 140 History 131 Historic sites 123 Trails 47 Historic buildings 46 Conservation and restoration 43 Antiquities 38 Management 25 Roads 25 Outdoor recreation 23 Indians of North America 21 Indigenous peoples 19 Homes 17 Homes and haunts 17 Environmental aspects 16 Planning 16 Excavations (Archaeology) 15 Buildings 14 Cultural property 14 Protection 14 Buildings, structures, etc 12 Recreation areas 12 Historic districts 10 Historic preservation 10 African Americans 9 Architecture 9 National monuments 9 Recreational use 9 Design and construction 8 Landscape architecture 8