Illinois - Criteria: C (architecture/engineering)
| Princeton North Main Street Historic District |
| Princeton South Main Street-Courthouse Square Historic District |
| Principia College Historic District |
| Proctor, John C., Recreation Center |
| Produce Terminal Cold Storage Company Building |
| Promontory Apartments |
| Public Service Building |
| Pulaski Park and Fieldhouse |
| Pullman Historic District |
| Pulsifer, Edward, House |
| Pure Oil Station |
| Purple, George E., House |
| Putnam County Courthouse |
| Quigley Preparatory Seminary |
| Quinby, Ivory, House |
| Quincy East End Historic District |
| Quincy Northwest Historic District |
| Ragdale |
| Railway Exchange Building |
| Rainey, Henry T., Farm |
| Ramsey, Charles N., and Herry E. Weese House |
| Ravenswood Manor Historic District |
| Raymond M. Hilliard Center Historic District |
| Raymond Park Apartments |
| Red Bud Historic District |
| Red Covered Bridge |
| Reebie Moving and Storage Company |
| Reed, Mrs. Kersey Coates, House |
| Reef House |
| Rees, Harriet F., House |
| Reid House |
| Reid Murdoch Building |
| Reimbold, William J., House |
| Reliance Building |
| Ridge Boulevard Apartments |
| Ridge Grove |
| Ridge Historic District |
| Ridgeland-Oak Park Historic District |
| Ridge Manor |
| Ridgewood |
| Riis, Jacob A., Park |
| Rippon-Kinsella House |
| Ritzman, William, House |
| Riverbank Laboratories |
| River Forest Historic District |
| Riverside Landscape Architecture District |
| Riverview Historic District |
| Robbins Park Historic District |
| Robertson, John, Jr., House |
| Roberts, William H., House |
| Robie, Frederick C., House |
| Robinson-Bonnett Inn |
| Robinson House |
| Robinson-Stewart House |
| Robinwood |
| Rochelle Downtown Historic District |
| Rockford Elk's Lodge #64 |
| Rockford Morning Star Building |
| Rock Island Arsenal |
| Rock Island Depot and Freight House |
| Rockton Historic District |
| Rockwell Mound |
| Rogers, Orson, House |
| Rogers Park Manor Bungalow Historic District |
| Rohrbough, Calendar, House |
| Roloson, Robert, Houses |
| Rookery Building |
| Rookwood Apartments |
| Roosevelt Junior High School |
| Root-Badger House |
| Ropp-Grabill House |
| Rosehill Cemetery Administration Building and Entry Gate |
| Rosenwald Apartment Building |
| Rosewood Park |
| Ross, Harvey Lee, House |
| Ross, Joseph, House |
| Rothschild, A. M., & Company Store |
| Roycemore School |
| Roytek, Richard, House |
| Rozek, Theodore, House |
| Rubens Rialto Square Theater |
| Ruebel Hotel |
| Rutherford, Dr. Hiram, House and Office |
| Ryan Round Barn |
| Sala Apartment Building |
| Sandwich City Hall |
| Sauganash Historic District |
| Scales Mound Historic District |
| Schertz, Joseph, House |
| Schiller, Alfred A.,House |
| Schlosser, Frank, Complex |
| Schoenhofen Brewery Historic District |
| Schorsch Irving Park Gardens Historic District |
| Schulze Baking Company Plant |
| Schurz, Carl, High School |
| Schweikher, Paul, House and Studio |
| Scott Field Historic District |
| Scott, Matthew T., House |
| Scott-Vrooman House |
| Scutt, Hiram B., Mansion |
Data from United States Park Service and Wikidata
