Colorado - Role: Building
| Ochsner Hospital |
| Office of Civil Defense Emergency Operations Center |
| Ogden Theatre |
| Old Ladore School |
| Old Livery Stable |
| Opera House Block/Central Block Building |
| Ore Processing Mill and Dam |
| Oriental Theater |
| Orlando Flats |
| Orman-Adams House |
| Osgood Castle |
| Osgood Gamekeeper's Lodge |
| Osgood-Kuhnhausen House |
| Ottesen Grain Company Feed Mill |
| Ouray City Hall and Walsh Library |
| Overland Cotton Mill |
| Owen Estate |
| Oxford Hotel |
| Oxford Hotel |
| Pacific Express Stable |
| Palace Hotel |
| Palmer-Ferril House |
| Palmer Hall |
| Palmer, Judge Peter L. House |
| Paonia First Christian Church |
| Paramount Theater |
| Parish, Harvey J., House |
| Paris Mill |
| Park County Courthouse and Jail |
| Park Point Fire Lookout |
| Park Theatre |
| Parry, William D., House |
| Patterson House |
| Pauline Chapel |
| Pearce-McAllister Cottage |
| Peck House |
| Pedro-Botz House |
| People's Methodist Episcopal Church |
| Peoples Presbyterian Church |
| Peterson House |
| Peters Paper Company Warehouse |
| Petrelli-DelPizzo House |
| Phillips County Courthouse |
| Phillips, Harry and Lilly, House |
| Photography and Armament School Buildings, Lowry Air Force Base |
| Pierce-Haley House |
| Pike's Peak Grange No. 163 |
| Pine Hall |
| Pioneer Cabin |
| Pioneer Sod House |
| Pipe Line School |
| Pitkin County Courthouse |
| Plaza Hotel |
| Pleasant Valley School |
| Pleasant Valley School |
| Plummer School |
| Poncha Springs Schoolhouse |
| Ponderosa Lodge |
| Powell and Blair Stone Ranch |
| Pride of the Rockies Flour Mill |
| Prowers County Building |
| Pryor, Frank, House |
| Public Service Building |
| Pueblo County Courthouse |
| Pueblo Federal Building |
| Quaintance Block |
| Quaker Flour Mill |
| Railway Exchange Addition and Railway Exchange New Building |
| Rankin Presbyterian Church |
| Ray Apartments Buildings |
| Raymond, Wilbur S., House |
| Redstone Inn |
| Reimer-Smith Oil Station |
| Rhoades House |
| Rialto Theater |
| Rice, Ida M., House |
| Rice, Ward, House |
| Richards Mansion |
| Richthofen Castle |
| Rico City Hall |
| Riede's City Bakery |
| Rimrock School |
| Robertson, T. H., House |
| Robidoux, M.J. Lavina, House |
| Robinson House |
| Robinson House |
| Robison Mansion |
| Rochester Hotel |
| Rock Creek Stage Station |
| Rockland Community Church and Cemetery |
| Rock Springs Ranger Station |
| Rocky Ford Post Office |
| Rocky Mountain Bank Note Company Building |
| Rocky Mountain Hotel |
| Rocky Mountain Mammoth Mine |
| Rocky Mountain National Park Administration Building |
| Romano, Samuel and Albina, House |
| Romeo Block |
| Rood Candy Company Building |
| Rooney Ranch |
Data from United States Park Service and Wikidata
