Illinois - Criteria: A (event)
| Nauvoo Historic District |
| New Masonic Building and Oriental Theater |
| New Orpheum Theatre |
| Nisbet Homestead Farm |
| Noble-Seymour-Crippen House |
| North Eighth Street Plaza |
| North Geneva Historic District |
| North Grove School |
| North Side Historic District |
| North Wells Street Historic District |
| Northwestern Terra Cotta Company Building |
| Norwood Park Historical District |
| Oak Hill Cemetery |
| Oaklawn Farm |
| Oak Park Conservatory |
| Oak Park Village Hall |
| Oak Ridge Apartments |
| Oakton Gables |
| Oakton Historic District |
| Odd Fellows Opera Block |
| Odell Building |
| Old Cahokia Courthouse |
| Old Chicago Historical Society Building |
| Old Colony Buildings |
| Old Danish Church |
| Old Fire Station |
| Old Iroquois County Courthouse |
| Old Main |
| Old Main, Augustana College |
| Old Main Building |
| Old Market House |
| Old Morrison Mill |
| Old State Capitol |
| Old Stone Arch Bridge |
| Old Stone Arch, National Road |
| Old Stone Gate of Chicago Union Stockyards |
| Old Stone Hotel |
| Old Town Triangle Historic District |
| Oliver Building |
| Olmstead Depot |
| Olney Carnegie Library |
| Olympia Fields Country Club |
| Oquawka Wagon Bridge |
| Orchestra Hall |
| Oregon Commercial Historic District |
| Oregon Public Library |
| Original Springs Hotel and Bathhouse |
| Otis Elevator Company Factory Building |
| Ottawa Commercial Historic District |
| Ottawa East Side Historic District |
| Otte, Dennis, Round Barn |
| Ouilmette North Historic District |
| Overton, Anthony, Elementary School |
| Overton Hygienic Building |
| Pacesetter Gardens Historic District |
| Palestine Commercial Historic District |
| Palmer Park |
| Paramount Theatre |
| Paris Carnegie Public Library |
| Paris Elks Lodge No. 812 Building |
| Parlin Library |
| Pattington Apartments |
| Patton, John, Log Cabin |
| Paxton Carnegie Public Library |
| Paxton First Schoolhouse |
| Peacock Brewery |
| Peck and Hills Furniture Company Warehouse |
| Pemberton Hall and Gymnasium |
| Peoples Gas Building |
| Peoples National Bank Building-Fries Building |
| Peoria Automobile Club |
| Peoria Cordage Company |
| Peoria Lock and Dam Historic District |
| Peoria Mineral Springs |
| Peoria State Hospital |
| Peoria Warehouse Historic District |
| Peoria Waterworks |
| Peotone Mill |
| Pere Marquette Hotel |
| Perry County Jail |
| Petersburg Historic District |
| Peterstown House |
| Phi Delta Theta Fraternity House |
| Phillips, Alfred, House |
| Phi Mu Sorority House |
| Phoenix Opera House Block |
| Pickwick Theater Building |
| Pilsen Historic District |
| Pine Grove Community Club |
| Pittsfield East School |
| Plainfield Halfway House |
| Plano Hotel |
| Pleasant Home |
| Poinsetta Apartments |
| Point School |
| Polish National Alliance Headquarters |
| Polish Roman Catholic Union of America |
| Polo Independent Order of Odd Fellows Lodge No. 197 |
| Pontiac City Hall and Fire Station |
| Portage Park |
Data from United States Park Service and Wikidata
