| Name | What | Region | Country | Lat | Long | Elev ft. | Pop est |
|---|---|---|---|---|---|---|---|
| On the Lake Park Mobile Home Park | city | Florida | United States | 29.04 | -81.96 | 72 | |
| On-a-Slant Village (historical) | city | North Dakota | United States | 46.77 | -100.85 | 1699 | |
| Ona | city | Florida | United States | 27.48 | -81.92 | 82 | |
| Ona | city | Oregon | United States | 44.50 | -124.02 | 196 | |
| Ona | city | West Virginia | United States | 38.42 | -82.21 | 830 | |
| Ona (historical) | city | Arkansas | United States | 34.55 | -91.55 | 213 | |
| Onaga | city | Kansas | United States | 39.49 | -96.17 | 1095 | |
| Onaka | city | South Dakota | United States | 45.19 | -99.47 | 1850 | |
| Onalaska | city | Texas | United States | 30.81 | -95.12 | 147 | |
| Onalaska | city | Washington | United States | 46.58 | -122.72 | 830 | |
| Onalaska | city | Wisconsin | United States | 43.88 | -91.24 | 830 | |
| Onalaska (historical) | city | Arkansas | United States | 33.67 | -92.74 | 127 | |
| Onamia | city | Minnesota | United States | 46.07 | -93.67 | 1249 | |
| Onan | city | Virginia | United States | 37.99 | -78.82 | 830 | |
| Onancock | city | Virginia | United States | 37.71 | -75.75 | 19 | |
| Onapa | city | Oklahoma | United States | 35.41 | -95.55 | 830 | |
| Onarga | city | Illinois | United States | 40.72 | -88.01 | 830 | |
| Onativia | city | New York | United States | 42.89 | -76.09 | 898 | |
| Onau (historical) | city | Hawaii | United States | 20.62 | -156.43 | 114 | |
| Onava | city | New Mexico | United States | 35.70 | -105.09 | 6709 | |
| Onawa | city | Iowa | United States | 42.03 | -96.10 | 1046 | |
| Onawa | city | Maine | United States | 45.37 | -69.37 | 830 | |
| Onawa Junction | city | Iowa | United States | 42.72 | -95.56 | 1240 | |
| Onaway | city | Idaho | United States | 46.93 | -116.89 | 2598 | |
| Onaway | city | Michigan | United States | 45.36 | -84.22 | 885 | |
| Onberg | city | Pennsylvania | United States | 40.67 | -79.06 | 1204 | |
| Onchiota | city | New York | United States | 44.49 | -74.12 | 1699 | |
| Onda | city | Arkansas | United States | 35.87 | -94.29 | 1699 | |
| One Hawkeye Mobile Home Park | city | Washington | United States | 48.09 | -122.82 | 196 | |
| One Hundred One Pines | city | Washington | United States | 47.31 | -122.04 | 830 | |
| One Hundred Palms | city | California | United States | 33.56 | -116.17 | -1689 | |
| One Hundred Thirty - Eighth Park Mobile Estates | city | Washington | United States | 47.13 | -122.45 | 328 | |
| One Hundred and One Ranch | city | Missouri | United States | 38.35 | -90.67 | 830 | |
| One Mile | city | Arizona | United States | 36.80 | -112.05 | 6003 | |
| One North Place | city | Louisiana | United States | 32.61 | -93.84 | 183 | |
| One River Place Colonia | city | Texas | United States | 27.40 | -99.48 | 400 | |
| Oneco | city | Connecticut | United States | 41.69 | -71.81 | 367 | |
| Oneco | city | Florida | United States | 27.45 | -82.55 | 22 | |
| Oneco | city | Illinois | United States | 42.49 | -89.66 | 849 | |
| Onega | city | Minnesota | United States | 47.32 | -92.83 | 1669 | |
| Onego | city | West Virginia | United States | 38.85 | -79.42 | 1899 | |
| Oneida | city | Arkansas | United States | 34.46 | -90.78 | 164 | |
| Oneida | city | Illinois | United States | 41.07 | -90.23 | 830 | |
| Oneida | city | Iowa | United States | 42.54 | -91.35 | 1033 | |
| Oneida | city | Kansas | United States | 39.86 | -95.94 | 1223 | |
| Oneida | city | Kentucky | United States | 37.27 | -83.65 | 889 | |
| Oneida | city | New York | United States | 43.09 | -75.65 | 830 | |
| Oneida | city | Ohio | United States | 39.48 | -84.39 | 830 | |
| Oneida | city | Ohio | United States | 40.70 | -81.15 | 1092 | |
| Oneida | city | Oklahoma | United States | 35.97 | -98.07 | 1099 | |
| Oneida | city | Pennsylvania | United States | 40.91 | -76.13 | 1696 | |
| Oneida | city | Pennsylvania | United States | 40.92 | -79.88 | 1072 | |
| Oneida | city | Tennessee | United States | 36.50 | -84.51 | 1669 | |
| Oneida | city | Washington | United States | 46.31 | -123.68 | 101 | |
| Oneida | city | Wisconsin | United States | 44.50 | -88.18 | 830 | |
| Oneida | city | Louisiana | United States | 30.02 | -90.80 | 13 | |
| Oneida Castle | city | New York | United States | 43.08 | -75.63 | 830 | |
| Oneida Center | city | Michigan | United States | 42.73 | -84.78 | 872 | |
| Oneida Corners | city | New York | United States | 43.38 | -73.63 | 314 | |
| Oneida Lake Beach East | city | New York | United States | 43.17 | -75.76 | 377 | |
| Oneida Lake Beach West | city | New York | United States | 43.16 | -75.85 | 396 | |
| Oneida Subdivision | city | Tennessee | United States | 35.87 | -85.09 | 1860 | |
| Oneida Valley | city | New York | United States | 43.15 | -75.72 | 383 | |
| Oneida Village Mobile Home Park | city | New York | United States | 42.45 | -75.11 | 1095 | |
| Oneill (historical) | city | Montana | United States | 46.15 | -105.15 | 2598 | |
| Onekama | city | Michigan | United States | 44.36 | -86.21 | 830 | |
| Onekama Junction | city | Michigan | United States | 44.34 | -86.20 | 862 | |
| Onemo | city | Virginia | United States | 37.40 | -76.27 | 3 | |
| Onenoa | city | American Samoa | United States | -14.26 | -170.58 | 3 | |
| Oneoneloa | city | American Samoa | United States | -14.31 | -170.69 | 0 | |
| Oneonta | city | Alabama | United States | 33.95 | -86.47 | 885 | |
| Oneonta | city | Kentucky | United States | 38.98 | -84.30 | 830 | |
| Oneonta | city | New York | United States | 42.45 | -75.06 | 1095 | |
| Oneonta (historical) | city | Kansas | United States | 39.65 | -97.88 | 1669 | |
| Oneota | city | Minnesota | United States | 46.75 | -92.17 | 830 | |
| Oneota (historical) | city | Nevada | United States | 37.94 | -118.29 | 7650 | |
| Oneota (historical) | city | Nevada | United States | 38.02 | -115.34 | 5029 | |
| Oneta | city | Oklahoma | United States | 36.02 | -95.71 | 830 | |
| Ong | city | Nebraska | United States | 40.40 | -97.84 | 1669 | |
| Ong | city | New Jersey | United States | 39.91 | -74.62 | 98 | |
| Ongeuidel | city | Palau | United States | 7.04 | 134.26 | 3 | |
| Ongo | city | Missouri | United States | 36.99 | -92.89 | 1669 | |
| Onia | city | Arkansas | United States | 35.92 | -92.33 | 843 | |
| Onida | city | South Dakota | United States | 44.71 | -100.06 | 1899 | |
| Onie (historical) | city | West Virginia | United States | 39.62 | -80.63 | 1669 | |
| Onigamiinsing | city | Minnesota | United States | 46.78 | -92.11 | 830 | |
| Onigum | city | Minnesota | United States | 47.11 | -94.54 | 1669 | |
| Onihitsk (historical) | city | Alaska | United States | 57.15 | -152.87 | 0 | |
| Onion Creek | city | Texas | United States | 32.22 | -96.62 | 377 | |
| Onion Creek | city | Washington | United States | 48.78 | -117.81 | 2591 | |
| Onion Creek | city | Texas | United States | 30.14 | -97.78 | 830 | |
| Onion Spring | city | Texas | United States | 29.40 | -103.33 | 3405 | |
| Oniontown | city | New York | United States | 41.72 | -73.58 | 396 | |
| Oniontown | city | New York | United States | 43.12 | -75.83 | 380 | |
| Oniontown | city | Pennsylvania | United States | 41.35 | -80.34 | 1115 | |
| Onks | city | Tennessee | United States | 36.30 | -82.44 | 1797 | |
| Onley | city | Virginia | United States | 37.69 | -75.72 | 42 | |
| Only | city | Missouri | United States | 37.92 | -92.95 | 1085 | |
| Only | city | Tennessee | United States | 35.86 | -87.69 | 830 | |
| Onnalinda | city | Pennsylvania | United States | 40.31 | -78.68 | 2509 | |
| Ono | city | California | United States | 40.48 | -122.62 | 918 | |
| Ono | city | Kentucky | United States | 36.99 | -84.97 | 902 | |
| Ono | city | Pennsylvania | United States | 40.40 | -76.53 | 830 | |
| Ono | city | Wisconsin | United States | 44.66 | -92.26 | 1148 | |
| Onomea (historical) | city | Hawaii | United States | 19.81 | -155.10 | 226 | |
| Onondaga | city | Michigan | United States | 42.44 | -84.56 | 898 | |
| Onondaga Castle | city | New York | United States | 42.97 | -76.14 | 830 | |
| Onondaga Hill | city | New York | United States | 43.00 | -76.18 | 830 | |
| Onongoch | city | Federated States of Micronesia | United States | 7.35 | 151.82 | 3 | |
| Onoqua (historical) | city | Alabama | United States | 32.47 | -86.44 | 295 | |
| Onota | city | Michigan | United States | 46.47 | -87.00 | 830 | |
| Onoto | city | West Virginia | United States | 38.27 | -80.11 | 2509 | |
| Onouli (historical) | city | Hawaii | United States | 19.52 | -155.92 | 1814 | |
| Onoville | city | New York | United States | 42.03 | -78.97 | 1669 | |
| Onset | city | Massachusetts | United States | 41.74 | -70.66 | 0 | |
| Onset Station | city | Massachusetts | United States | 41.76 | -70.68 | 9 | |
| Onslow | city | Iowa | United States | 42.11 | -91.02 | 872 | |
| Onslow | city | Washington | United States | 47.17 | -124.11 | 85 | |
| Onslow Gardens | city | North Carolina | United States | 34.78 | -77.42 | 29 | |
| Onspaugh Corners | city | Pennsylvania | United States | 41.65 | -80.21 | 1171 | |
| Onstad Trailer Park | city | Minnesota | United States | 43.56 | -91.64 | 1669 | |
| Onsted | city | Michigan | United States | 42.01 | -84.19 | 987 | |
| Onstott Acres | city | Florida | United States | 27.67 | -82.40 | 9 | |
| Ontario | city | Illinois | United States | 41.08 | -90.31 | 830 | |
| Ontario | city | Indiana | United States | 41.70 | -85.38 | 895 | |
| Ontario | city | Iowa | United States | 42.04 | -93.68 | 997 | |
| Ontario | city | Kansas | United States | 39.57 | -95.88 | 1164 | |
| Ontario | city | New York | United States | 43.22 | -77.28 | 830 | |
| Ontario | city | Ohio | United States | 40.76 | -82.59 | 1669 | |
| Ontario | city | Oregon | United States | 44.03 | -116.96 | 2509 | |
| Ontario | city | Pennsylvania | United States | 40.10 | -80.07 | 1095 | |
| Ontario | city | Utah | United States | 40.75 | -111.90 | 4284 | |
| Ontario | city | Virginia | United States | 36.99 | -78.49 | 830 | |
| Ontario | city | Wisconsin | United States | 43.73 | -90.59 | 882 | |
| Ontario | city | California | United States | 34.06 | -117.65 | 990 | |
| Ontario Beach | city | New York | United States | 43.26 | -77.61 | 262 | |
| Ontario Center | city | New York | United States | 43.23 | -77.31 | 830 | |
| Ontario Heights | city | Oregon | United States | 44.07 | -117.02 | 2509 | |
| Ontario Place Mobile Home Park | city | Michigan | United States | 41.77 | -86.23 | 830 | |
| Ontario on the Lake | city | New York | United States | 43.28 | -77.35 | 298 | |
| Ontarioville | city | Illinois | United States | 41.99 | -88.15 | 830 | |
| Ontelaunee | city | Pennsylvania | United States | 40.42 | -75.94 | 298 | |
| Ontelaunee Heights | city | Pennsylvania | United States | 40.45 | -75.89 | 357 | |
| Onteo Beach | city | New York | United States | 43.36 | -77.91 | 246 | |
| Onteora Park | city | New York | United States | 42.22 | -74.14 | 2509 | |
| Onton | city | Kentucky | United States | 37.56 | -87.44 | 830 | |
| Ontonagon | city | Michigan | United States | 46.87 | -89.31 | 830 | |
| Onvil | city | North Carolina | United States | 35.28 | -79.87 | 830 | |
| Onville (historical) | city | Virginia | United States | 38.49 | -77.44 | 147 | |
| Onward | city | Indiana | United States | 40.69 | -86.19 | 830 | |
| Onward | city | Mississippi | United States | 32.73 | -90.94 | 98 | |
| Onway Lake | city | New Hampshire | United States | 43.03 | -71.22 | 265 | |
| Onycha | city | Alabama | United States | 31.21 | -86.28 | 337 | |
| Onyx | city | Arkansas | United States | 34.85 | -93.41 | 830 | |
| Onyx | city | California | United States | 35.69 | -118.22 | 2821 |