Iowa - Criteria: C (architecture/engineering)
| Pucker Street Historic District |
| Purdy, Eliphalet W. and Catherine E. Jaquish, House |
| Putnam-Parker Block |
| Pyle, Glenn O. and Lucy O., House |
| Quail Avenue Bridge |
| Quarry Bridge |
| Quasdorf Blacksmith and Wagon Shop |
| Queen, Hogan and Martha A. Runkle, House |
| Quickel, Jacob, House |
| Radcliff, Willam, House |
| Raible, F. J., House |
| Ranshaw, Samuel and Emma A., House |
| Ranzow-Sander House |
| Raphael, Jacob, Building |
| Rath, Johann Christian Frederick, House |
| Ray, Frank G., House & Carriage House |
| Raymond, P. P., House |
| Read Township Culvert |
| Reburn, Thomas, Polygonal Barn |
| Rector, Jason and Elizabeth Baylor, House |
| Red Ball Garage |
| Red Bridge |
| Red Bridge |
| Redmond Park-Grande Avenue Historic District |
| Red Oak Downtown Historic District |
| Red Oak Grove Presbyterian Church and Cemetery |
| Red Oak Public Library |
| Redstone |
| Reeve, Leander, House |
| Reeves, Isaac and Agnes (Bells), House |
| Regina Coeli Monastery |
| Register and Tribune Building |
| Reichert, John Christian and Bertha Landrock, House |
| Renken, Renke and Wubke, House |
| Renwick Building |
| Renwick House |
| Reverend Little's Young Ladies Seminary |
| Rewerts, George, House |
| Reynolds, Charles B., Round Barn |
| Richardson-Jakway House |
| Ricker, B. J., House |
| Rick's Brewery |
| Riekenberg, J. H., House |
| Ringgold County Courthouse |
| Ringgold County Jail |
| Rittenmeyer, F. X., House |
| River Street Bridge |
| River Street Bridge |
| Riverview Park Plat Historic District |
| Riverview Terrace Historic District |
| Robb House and Spring House |
| Roberts, Edward C., House |
| Roberts Octagon Barn |
| Robin Avenue Bridge |
| Rock Crest-Rock Glen Historic District |
| Rock Falls Bridge |
| Rockford Mill |
| Rock Island Passenger Depot |
| Rockwell City Bridge |
| Rogers, George W. Company Shot Tower |
| Roling, Henry, House |
| Rollins, Ralph, House |
| Romey, George, House |
| Roosevelt Elementary School |
| Roosevelt School |
| Rose Hill |
| Rose Hill Historic District |
| Rose Hill Methodist Episcopal Church |
| Roseman Covered Bridge |
| Roshek Brothers Department Store |
| Roslyn Flats |
| Ross Grain Elevator |
| Round Barn, Bruce Township Section 3 |
| Round Barn, Buckingham Township |
| Round Barn, Cooper Township |
| Round Barn, Dubuque Township |
| Round Barn, Millville Township |
| Round Barn, Norway Township |
| Round Barn, Pilot Grove Township |
| Round Barn, Washington Township |
| Round Barn, Washington Township |
| Rowhouses at 702-712 Kirkwood Boulevard |
| Royal Neighbors of America National Home Historic District |
| Rule, Duncan, House |
| Russell, Rensselaer, House |
| Rye, Chris, House |
| Sac City Chicago and North Western Depot |
| Sac City Monument Square Historic District |
| Sac County Courthouse |
| Sacred Heart Roman Catholic Cathedral Complex |
| Sacred Heart School |
| Saint Barnabas Episcopal Church |
| Saint Boniface Church |
| Saint Irenaeus Church |
| Saint John's Roman Catholic Church |
| Saint Patrick's Catholic Church and Rectory |
| Saint Patrick's Roman Catholic Church |
| Saints Peter and Paul Catholic Church |
| Saints Peter and Paul Catholic Church |
| Saints Peter and Paul Church |
Data from United States Park Service and Wikidata
