| Name | What | Region | Country | Lat | Long | Elev Ft. | Pop Est |
|---|
| O'Leary | city | Iowa | United States | 42.70667 | -96.05833 | 1400 | 574 |
| O'Neill | city | Iowa | United States | 42.60889 | -90.88667 | 853 | 1544 |
| Oakdale | city | Iowa | United States | 41.70639 | -91.60278 | 784 | 24450 |
| Oakfield | city | Iowa | United States | 41.53333 | -94.9075 | 1299 | 642 |
| Oakland | city | Iowa | United States | 41.30917 | -95.39639 | 1181 | 705 |
| Oakland | city | Iowa | United States | 42.58111 | -93.44306 | 1141 | 563 |
| Oakland Acres | city | Iowa | United States | 41.71722 | -92.82028 | 948 | 2407 |
| Oakland Mills | city | Iowa | United States | 40.93611 | -91.61639 | 574 | 4561 |
| Oakley | city | Iowa | United States | 41.10111 | -93.365 | 951 | 1110 |
| Oakville | city | Iowa | United States | 41.09972 | -91.04444 | 547 | 1516 |
| Oakwood | city | Iowa | United States | 43.00917 | -92.77694 | 1046 | 1090 |
| Oakwood Station historical | city | Iowa | United States | 41.93722 | -93.51611 | 918 | 2972 |
| Oasis | city | Iowa | United States | 41.70611 | -91.38528 | 839 | 1477 |
| Ocheyedan | city | Iowa | United States | 43.41611 | -95.53444 | 1535 | 518 |
| Odebolt | city | Iowa | United States | 42.31222 | -95.25028 | 1400 | 826 |
| Oelwein | city | Iowa | United States | 42.67333 | -91.91333 | 1049 | 7336 |
| Ogden | city | Iowa | United States | 42.03917 | -94.0275 | 1099 | 902 |
| Okoboji | city | Iowa | United States | 43.38639 | -95.14806 | 1400 | 7083 |
| Olaf | city | Iowa | United States | 42.88667 | -93.72444 | 1249 | 803 |
| Old Balltown | city | Iowa | United States | 42.63167 | -90.85833 | 997 | 1255 |
| Old Peru | city | Iowa | United States | 41.23583 | -93.945 | 994 | 544 |
| Old Town | city | Iowa | United States | 43.31361 | -95.14389 | 1400 | 2572 |
| Old Tripoli | city | Iowa | United States | 42.82611 | -92.26528 | 1056 | 1021 |
| Olds | city | Iowa | United States | 41.13417 | -91.54472 | 715 | 1012 |
| Olin | city | Iowa | United States | 41.99806 | -91.14139 | 807 | 1045 |
| Olivet | city | Iowa | United States | 41.31361 | -92.83 | 843 | 911 |
| Ollie | city | Iowa | United States | 41.19806 | -92.09222 | 800 | 746 |
| Olmitz | city | Iowa | United States | 41.08167 | -93.16917 | 921 | 532 |
| Onawa | city | Iowa | United States | 42.02667 | -96.09694 | 1046 | 3348 |
| Onawa Junction | city | Iowa | United States | 42.725 | -95.5575 | 1240 | 4870 |
| Oneida | city | Iowa | United States | 42.54278 | -91.35333 | 1033 | 1132 |
| Onslow | city | Iowa | United States | 42.10694 | -91.015 | 872 | 876 |
| Ontario | city | Iowa | United States | 42.03583 | -93.68139 | 997 | 32929 |
| Oralabor | city | Iowa | United States | 41.7 | -93.58778 | 951 | 36507 |
| Oran | city | Iowa | United States | 42.70139 | -92.07444 | 1066 | 924 |
| Orange | city | Iowa | United States | 42.42583 | -92.35639 | 951 | 36883 |
| Orange City | city | Iowa | United States | 43.00722 | -96.05806 | 1400 | 6335 |
| Orchard | city | Iowa | United States | 43.2275 | -92.77194 | 1076 | 2236 |
| Orchard Park Mobile Home Court | city | Iowa | United States | 43.145 | -93.37278 | 1220 | 4875 |
| Ord | city | Iowa | United States | 41.25111 | -94.07083 | 1161 | 1537 |
| Orient | city | Iowa | United States | 41.20306 | -94.41444 | 1302 | 368 |
| Orillia | city | Iowa | United States | 41.50972 | -93.72861 | 928 | 25649 |
| Orleans | city | Iowa | United States | 43.44722 | -95.09222 | 1427 | 5499 |
| Orleans | city | Iowa | United States | 40.72556 | -92.65722 | 961 | 789 |
| Ormanville | city | Iowa | United States | 40.90861 | -92.48306 | 748 | 905 |
| Orson | city | Iowa | United States | 41.77944 | -95.98306 | 1040 | 802 |
| Orton | city | Iowa | United States | 41.58861 | -95.81 | 1092 | 1028 |
| Ortonville | city | Iowa | United States | 41.615 | -93.95944 | 1030 | 4106 |
| Osage | city | Iowa | United States | 43.28417 | -92.81083 | 1164 | 4396 |
| Osborne | city | Iowa | United States | 42.79194 | -91.44528 | 797 | 1055 |
| Osceola | city | Iowa | United States | 41.03389 | -93.76528 | 1105 | 4592 |
| Osgood | city | Iowa | United States | 43.19333 | -94.70111 | 1236 | 2428 |
| Oskaloosa | city | Iowa | United States | 41.29639 | -92.64417 | 856 | 11695 |
| Ossian | city | Iowa | United States | 43.14639 | -91.76444 | 1256 | 886 |
| Osterdock | city | Iowa | United States | 42.73361 | -91.15778 | 666 | 1011 |
| Oswalt | city | Iowa | United States | 41.69583 | -93.2975 | 780 | 1775 |
| Otho | city | Iowa | United States | 42.42472 | -94.15 | 1118 | 6128 |
| Otis | city | Iowa | United States | 41.95139 | -91.62306 | 711 | 28371 |
| Otley | city | Iowa | United States | 41.45889 | -93.03556 | 849 | 1104 |
| Oto | city | Iowa | United States | 42.28389 | -95.89278 | 1076 | 682 |
| Otranto | city | Iowa | United States | 43.45833 | -92.98556 | 1118 | 797 |
| Ottawa | city | Iowa | United States | 41.03 | -93.59083 | 1082 | 422 |
| Ottawa | city | Iowa | United States | 41.31194 | -93.50194 | 816 | 5576 |
| Otter Creek | city | Iowa | United States | 42.24056 | -90.6825 | 987 | 661 |
| Otterville | city | Iowa | United States | 42.50861 | -91.94639 | 948 | 4243 |
| Ottosen | city | Iowa | United States | 42.895 | -94.37972 | 1141 | 566 |
| Ottumwa | city | Iowa | United States | 41.00417 | -92.37361 | 656 | 11339 |
| Ottumwa Junction | city | Iowa | United States | 41.04833 | -92.43944 | 711 | 15122 |
| Overland Mobile Home Park | city | Iowa | United States | 41.25111 | -95.89444 | 977 | 84634 |
| Ovia | city | Iowa | United States | 40.855 | -93.3175 | 1053 | 604 |
| Owasa | city | Iowa | United States | 42.43361 | -93.20694 | 1118 | 1404 |
| Owego | city | Iowa | United States | 42.27944 | -96.15417 | 1069 | 648 |
| Owen | city | Iowa | United States | 43.0375 | -93.08194 | 1145 | 712 |
| Oxford | city | Iowa | United States | 41.72333 | -91.79028 | 774 | 3271 |
| Oxford Junction | city | Iowa | United States | 41.98361 | -90.95611 | 734 | 918 |
| Oxford Mills | city | Iowa | United States | 41.97028 | -90.95972 | 793 | 951 |
| Oyens | city | Iowa | United States | 42.82028 | -96.0575 | 1292 | 1408 |
| Ozark | city | Iowa | United States | 42.19528 | -90.87528 | 830 | 648 |
| Ozark historical | city | Iowa | United States | 42.1575 | -90.87417 | 797 | 602 |
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