Feature Name | Class | Elev. meters | County | Latitude DMS | Longitude DMS |
| Ogden School | School | 93 | New Madrid | 36 44 39 N | 089 33 21 W |
| Ogg School | School | 300 | Ray | 39 17 49 N | 094 05 36 W |
| Oggs Mill | Locale | 266 | Ray | 39 17 50 N | 094 05 10 W |
| Ogle Grove Cemetery | Cemetery | 308 | DeKalb | 39 56 42 N | 094 34 52 W |
| Ogle School (historical) | School | 306 | DeKalb | 39 54 04 N | 094 28 25 W |
| Ogles Hill | Summit | 241 | St. Clair | 38 04 15 N | 093 56 33 W |
| Ogles Lake Dam | Dam | 143 | Jefferson | 38 14 24 N | 090 26 54 W |
| Oglesville | Populated Place | 98 | Butler | 36 34 49 N | 090 18 37 W |
| Ohio | Populated Place | 255 | St. Clair | 38 09 20 N | 093 51 07 W |
| Ohio Cemetery | Cemetery | 299 | Nodaway | 40 26 27 N | 095 04 08 W |
| Ohio River | Stream | | Mississippi | 36 59 12 N | 089 07 50 W |
| Ohio School (historical) | School | 256 | St. Clair | 38 09 17 N | 093 51 05 W |
| Ohlendorf County Park | Park | 142 | St. Louis | 38 32 33 N | 090 18 10 W |
| Ohlman | Populated Place | 375 | Reynolds | 37 25 35 N | 091 06 55 W |
| Ohlman Church | Church | 374 | Reynolds | 37 25 26 N | 091 06 37 W |
| Oil City | Populated Place | 191 | Chariton | 39 20 40 N | 092 50 58 W |
| Oil Creek | Stream | | Cass | 38 51 48 N | 094 31 21 W |
| Ojibway (historical) | Locale | 111 | Wayne | 36 58 24 N | 090 24 32 W |
| OK School (historical) | School | 471 | Barry | 36 35 02 N | 094 00 28 W |
| Okaydy Reservoir Dam | Dam | 185 | Howard | 39 01 08 N | 092 45 15 W |
| Okete | Populated Place | 232 | Lincoln | 39 05 52 N | 090 55 49 W |
| Okkapassa Dam | Dam | 230 | Reynolds | 37 27 30 N | 090 48 00 W |
| Oklahoma Church | Church | 252 | Osage | 38 30 43 N | 091 43 05 W |
| Oklahoma School | School | 239 | Franklin | 38 13 51 N | 090 59 05 W |
| Oklahoma School | School | 231 | Franklin | 38 15 23 N | 090 59 01 W |
| Oklahoma School (historical) | School | 287 | Adair | 40 05 05 N | 092 29 47 W |
| Oklahoma School (historical) | School | 411 | Barry | 36 43 29 N | 094 00 32 W |
| Oklahoma School (historical) | School | 241 | Knox | 40 04 54 N | 092 06 54 W |
| Okland School | School | 214 | Howard | 39 08 28 N | 092 34 45 W |
| Oland Church | Church | 339 | Harrison | 40 32 34 N | 093 57 53 W |
| Olathia | Populated Place | 380 | Douglas | 37 01 38 N | 092 31 11 W |
| Old Alexandria Church | Church | 215 | Lincoln | 39 02 48 N | 090 58 17 W |
| Old Appleton | Populated Place | 125 | Cape Girardeau | 37 35 50 N | 089 42 46 W |
| Old Argo School (historical) | School | 275 | Franklin | 38 13 31 N | 091 20 23 W |
| Old Ashley Cemetery | Cemetery | 224 | Pike | 39 14 56 N | 091 13 04 W |
| Old Auxvasse Church | Church | 241 | Callaway | 38 57 01 N | 091 51 04 W |
| Old Baptist Church | Church | 300 | Hickory | 38 03 18 N | 093 16 51 W |
| Old Baptist Church Cemetery | Cemetery | 250 | Washington | 38 01 18 N | 090 45 21 W |
| Old Beaufort School | School | 224 | Franklin | 38 26 18 N | 091 13 31 W |
| Old Bethel Cemetery | Cemetery | 150 | Stoddard | 36 46 39 N | 090 00 23 W |
| Old Blackwell Cemetery | Cemetery | 186 | St. Francois | 38 03 43 N | 090 37 02 W |
| Old Bland | Populated Place | 247 | Gasconade | 38 18 54 N | 091 37 23 W |
| Old Bland Cemetery | Cemetery | 251 | Gasconade | 38 18 45 N | 091 37 35 W |
| Old Bland Creek | Stream | | Gasconade | 38 20 26 N | 091 37 22 W |
| Old Bland School (historical) | School | 236 | Gasconade | 38 18 41 N | 091 37 26 W |
| Old Bollinger Cemetery | Cemetery | 209 | Bollinger | 37 31 38 N | 089 56 22 W |
| Old Bowling Green Reservoir Dam | Dam | 225 | Pike | 39 20 36 N | 091 09 43 W |
| Old Brick Church | Church | 222 | Shelby | 39 51 43 N | 091 54 10 W |
| Old Busby Cemetery | Cemetery | 297 | Putnam | 40 28 18 N | 093 20 51 W |
| Old Buzzard School (historical) | School | 271 | Knox | 40 17 45 N | 092 19 24 W |
| Old Caney Basin | Basin | 98 | Scott | 37 07 38 N | 089 43 03 W |
| Old Caney Fork Cemetery | Cemetery | 158 | Cape Girardeau | 37 29 29 N | 089 48 23 W |
| Old Catholic Cemetery | Cemetery | 226 | Cole | 38 32 09 N | 092 19 57 W |
| Old Catholic Church (historical) | Church | 227 | Cole | 38 32 10 N | 092 19 57 W |
| Old Cemetery | Cemetery | 238 | Howard | 39 08 35 N | 092 36 07 W |
| Old Channel Big Creek | Stream | | Johnson | 38 33 54 N | 093 58 23 W |
| Old Channel Chariton River | Stream | | Chariton | 39 15 18 N | 092 51 41 W |
| Old Channel Davis Creek | Stream | | Saline | 38 59 35 N | 093 29 11 W |
| Old Channel Hubble Creek | Stream | | Cape Girardeau | 37 10 21 N | 089 41 34 W |
| Old Channel Little River | Stream | | Dunklin | 36 03 39 N | 090 05 26 W |
| Old Channel Little River | Stream | | Pemiscot | 36 14 01 N | 089 53 02 W |
| Old Channel Little Tarkio Creek | Stream | | Holt | 40 00 58 N | 095 15 51 W |
| Old Channel Missouri River | Stream | | Clay | 39 07 34 N | 094 26 59 W |
| Old Channel Nishnabotna River | Stream | | Atchison | 40 15 51 N | 095 30 43 W |
| Old Channel North Fabius River | Stream | | Lewis | 40 10 01 N | 091 46 11 W |
| Old Channel North Fabius River | Stream | | Marion | 39 53 38 N | 091 27 47 W |
| Old Channel North Fork Salt River | Stream | | Shelby | 39 51 04 N | 092 15 34 W |
| Old Channel North Wyaconda River | Stream | | Scotland | 40 25 51 N | 091 53 07 W |
| Old Channel Salt Creek | Stream | | Howard | 38 59 41 N | 092 52 01 W |
| Old Channel South Fabius River | Stream | | Lewis | 39 57 12 N | 091 54 24 W |
| Old Channel South Grand River | Stream | | Henry | 38 25 54 N | 093 58 16 W |
| Old Channel South Wyaconda River | Stream | | Scotland | 40 25 17 N | 091 55 12 W |
| Old Channel Tarkio River | Stream | | Holt | 40 01 18 N | 095 18 54 W |
| Old Channel Thompson River | Stream | | Grundy | 40 00 00 N | 093 36 44 W |
| Old Channel Varney River | Stream | | Dunklin | 36 09 14 N | 090 13 51 W |
| Old Channel Wakenda Creek | Stream | | Carroll | 39 20 54 N | 093 31 32 W |
| Old Channel Weldon River | Stream | | Grundy | 40 07 55 N | 093 38 10 W |
| Old Channel Wyaconda River | Stream | | Lewis | 40 13 43 N | 091 38 37 W |
| Old Chariton Cemetery | Cemetery | 263 | Macon | 39 50 39 N | 092 38 11 W |
| Old Chilhowee | Populated Place | 272 | Johnson | 38 36 23 N | 093 51 03 W |
| Old Christy Mine | Mine | 285 | Crawford | 38 01 27 N | 091 05 54 W |
| Old City Cemetery | Cemetery | 247 | Grundy | 40 04 07 N | 093 36 58 W |
| Old City Reservoir | Reservoir | 210 | Howard | 39 08 24 N | 092 42 31 W |
| Old Coldwater Cemetery | Cemetery | 76 | Dunklin | 36 04 03 N | 090 09 04 W |
| Old Coldwater Cemetery | Cemetery | 77 | Dunklin | 36 04 06 N | 090 09 00 W |
| Old Coldwater Church (historical) | Church | 77 | Dunklin | 36 04 09 N | 090 09 03 W |
| Old Concord Cemetery | Cemetery | 270 | Bollinger | 37 27 57 N | 090 06 02 W |
| Old Concord Cemetery | Cemetery | 368 | Texas | 37 22 44 N | 092 10 45 W |
| Old Copper Hill Iron Bank | Mine | 206 | Crawford | 38 11 41 N | 091 06 33 W |
| Old Covered Bridge (historical) | Bridge | 146 | Marion | 39 49 11 N | 091 30 51 W |
| Old Dallas School | School | 391 | Webster | 37 14 49 N | 093 00 29 W |
| Old Davis Cemetery | Cemetery | 214 | Lincoln | 38 55 35 N | 091 03 50 W |
| Old Ditch School (historical) | School | 215 | Jefferson | 38 12 35 N | 090 45 14 W |
| Old Elizabeth School (historical) | School | 210 | Miller | 38 17 43 N | 092 16 17 W |
| Old Elm Tree Church | Church | 392 | Stone | 36 33 15 N | 093 26 17 W |
| Old Erie Cemetery | Cemetery | 283 | Camden | 38 05 15 N | 092 44 16 W |
| Old Evening Shade | Locale | 367 | Texas | 37 35 39 N | 092 10 39 W |
| Old Field Hollow | Valley | | Oregon | 36 48 11 N | 091 32 55 W |
| Old Folks Pond | Lake | 223 | Vernon | 38 00 32 N | 094 04 56 W |
| Old Foot Ridge | Ridge | 372 | McDonald | 36 39 38 N | 094 14 49 W |
| Old Franklin Ditch | Canal | 77 | Pemiscot | 36 02 56 N | 089 45 53 W |
| Old Fredonia | Locale | 223 | Benton | 38 14 38 N | 093 15 60 W |
| Old German Cemetery | Cemetery | 219 | Clark | 40 21 41 N | 091 50 03 W |
| Old German Cemetery | Cemetery | 189 | Jefferson | 38 05 36 N | 090 27 33 W |
| Old Goss School (historical) | Locale | 362 | Dallas | 37 25 24 N | 093 06 36 W |
| Old Greenville (historical) | Populated Place | 115 | Wayne | 37 06 03 N | 090 27 17 W |
| Old Greenville Cemetery | Cemetery | 116 | Wayne | 37 06 05 N | 090 27 29 W |
| Old Greenville Recreation Area | Park | 115 | Wayne | 37 06 05 N | 090 27 12 W |
| Old Grove School | School | 237 | Franklin | 38 21 06 N | 091 15 52 W |
| Old Hamilton Works | Locale | 208 | Washington | 38 10 06 N | 091 04 08 W |