Feature Name | Class | Elev. meters | County | Latitude DMS | Longitude DMS |
| Thompson Cemetery | Cemetery | 219 | Jefferson | 40 54 56 N | 091 58 39 W |
| Thompson Cemetery | Cemetery | 188 | Louisa | 41 15 48 N | 091 13 35 W |
| Thompson Cemetery | Cemetery | 358 | Ringgold | 40 39 48 N | 094 13 19 W |
| Thompson Corner | Populated Place | 366 | Allamakee | 43 15 59 N | 091 13 50 W |
| Thompson Corner Cemetery | Cemetery | 348 | Allamakee | 43 15 40 N | 091 13 48 W |
| Thompson Creek | Stream | | Adams | 41 08 12 N | 094 42 13 W |
| Thompson Creek | Stream | | Harrison | 41 44 06 N | 095 49 06 W |
| Thompson Fire Department | Building | 389 | Winnebago | 43 22 14 N | 093 46 16 W |
| Thompson Grave | Cemetery | 248 | Wapello | 41 08 20 N | 092 29 41 W |
| Thompson Hall | Building | 344 | Hardin | 42 31 41 N | 093 16 07 W |
| Thompson Post Office | Post Office | 388 | Winnebago | 43 22 15 N | 093 46 16 W |
| Thompson Post Office (historical) | Post Office | 451 | Audubon | 41 49 50 N | 094 55 01 W |
| Thompson Public Library | Building | 389 | Winnebago | 43 22 14 N | 093 46 16 W |
| Thompson Roadside Prairie | Area | 381 | Winnebago | 43 23 08 N | 093 46 29 W |
| Thompsonville Post Office (historical) | Post Office | 281 | Monroe | 41 09 12 N | 093 00 41 W |
| Thomson Cemetery | Cemetery | 206 | Van Buren | 40 39 44 N | 091 50 38 W |
| Thomson Marsh Wildlife Management Area | Park | 377 | Howard | 43 18 15 N | 092 09 11 W |
| Thor | Populated Place | 347 | Humboldt | 42 41 17 N | 094 02 58 W |
| Thor (historical) | Locale | 350 | Humboldt | 42 41 28 N | 094 02 58 W |
| Thor City Hall | Building | 347 | Humboldt | 42 41 17 N | 094 02 58 W |
| Thor Fire Department | Building | 347 | Humboldt | 42 41 17 N | 094 02 58 W |
| Thor Post Office | Post Office | 347 | Humboldt | 42 41 17 N | 094 02 58 W |
| Thoreson Memorial Park | Park | 403 | Emmet | 43 24 30 N | 094 49 22 W |
| Thorman Park | Park | 434 | O'Brien | 43 10 22 N | 095 50 36 W |
| Thorn Apple Woods | Park | 305 | Franklin | 42 48 55 N | 093 03 21 W |
| Thorn School | School | 307 | Warren | 41 10 36 N | 093 34 41 W |
| Thornburg | Populated Place | 268 | Keokuk | 41 27 17 N | 092 20 09 W |
| Thornburg (historical) | Locale | 268 | Keokuk | 41 27 30 N | 092 19 47 W |
| Thornburg Post Office | Post Office | 268 | Keokuk | 41 27 17 N | 092 20 09 W |
| Thornton | Locale | 362 | Cerro Gordo | 42 56 38 N | 093 22 54 W |
| Thornton | Populated Place | 362 | Cerro Gordo | 42 56 41 N | 093 23 05 W |
| Thornton Cemetery | Cemetery | 311 | Dallas | 41 33 25 N | 093 55 48 W |
| Thornton Manor Nursing Center | Hospital | 210 | Allamakee | 43 21 36 N | 091 14 05 W |
| Thornton Post Office | Post Office | 363 | Cerro Gordo | 42 56 40 N | 093 22 59 W |
| Thornton Public Library | Building | 363 | Cerro Gordo | 42 56 38 N | 093 23 03 W |
| Thornton Town Hall | Building | 363 | Cerro Gordo | 42 56 38 N | 093 23 02 W |
| Thorpe | Populated Place | 311 | Delaware | 42 33 58 N | 091 26 58 W |
| Thorpe (historical) | Locale | 318 | Delaware | 42 33 45 N | 091 27 01 W |
| Thorpe Cemetery | Cemetery | 231 | Wapello | 41 04 00 N | 092 37 51 W |
| Thorpe Park | Park | 393 | Winnebago | 43 15 30 N | 093 45 19 W |
| Thorpe Post Office (historical) | Post Office | 311 | Delaware | 42 33 58 N | 091 26 58 W |
| Thorpe Union Cemetery | Cemetery | 311 | Delaware | 42 33 50 N | 091 28 13 W |
| Thorson Hall | Building | 390 | Winnebago | 43 15 47 N | 093 38 24 W |
| Thoten | Populated Place | 368 | Winneshiek | 43 18 35 N | 091 38 24 W |
| Thoten Post Office (historical) | Post Office | 368 | Winneshiek | 43 18 35 N | 091 38 24 W |
| Thrall | Locale | 343 | Wright | 42 45 41 N | 093 55 33 W |
| Thrall Post Office (historical) | Post Office | 343 | Wright | 42 45 41 N | 093 55 33 W |
| Three Bridges County Park | Park | 258 | Marshall | 42 01 40 N | 092 48 31 W |
| Three Early Trails Historical Marker | Park | 367 | Mills | 41 01 50 N | 095 40 16 W |
| Three Elms County Park | Park | 271 | Buchanan | 42 27 20 N | 091 52 04 W |
| Three Fingers Campground | Locale | 375 | Winnebago | 43 16 40 N | 093 42 21 W |
| Three Mile Lake | Reservoir | 343 | Union | 41 03 55 N | 094 12 26 W |
| Three Mile Lake Wildlife Management Area | Park | 361 | Union | 41 05 00 N | 094 14 01 W |
| Three Rivers Park | Park | 277 | Bremer | 42 44 10 N | 092 28 06 W |
| Three Rivers Trail | Trail | 333 | Humboldt | 42 43 25 N | 094 12 26 W |
| Three Rivers Wildlife Area | Park | 308 | Harrison | 41 48 22 N | 096 03 41 W |
| Three Water Wildlife Area | Park | 387 | Buena Vista | 42 38 40 N | 095 02 56 W |
| Three-Thirty Golf and Country Club | Locale | 230 | Cedar | 41 51 30 N | 090 54 56 W |
| Threemile Creek | Stream | | Cass | 41 09 33 N | 094 57 52 W |
| Threemile Creek | Stream | | Union | 41 02 10 N | 094 06 42 W |
| Threemile Creek | Stream | | Woodbury | 42 26 18 N | 095 49 50 W |
| Thunder Creek | Stream | | Mahaska | 41 27 50 N | 092 52 17 W |
| Thunder Ridge Mall | Locale | 297 | Black Hawk | 42 32 17 N | 092 28 23 W |
| Thunder Woman County Park | Park | 267 | Black Hawk | 42 37 54 N | 092 32 11 W |
| Thunderhills Golf and Country Club | Locale | 335 | Dubuque | 42 27 05 N | 090 49 00 W |
| Thunderwoman Grave Site Historical Marker | Park | 280 | Black Hawk | 42 37 60 N | 092 29 26 W |
| Thurman | Populated Place | 298 | Fremont | 40 49 12 N | 095 44 52 W |
| Thurman Cemetery | Cemetery | 355 | Fremont | 40 49 49 N | 095 44 04 W |
| Thurman Cemetery | Cemetery | 355 | Fremont | 40 49 50 N | 095 44 04 W |
| Thurman Post Office | Post Office | 298 | Fremont | 40 49 12 N | 095 44 52 W |
| Tibbetts Creek | Stream | | Jones | 42 14 03 N | 091 07 16 W |
| Tibbitt Post Office (historical) | Post Office | 248 | Polk | 41 47 30 N | 093 25 31 W |
| Tibbitts Park | Park | 261 | Black Hawk | 42 31 37 N | 092 22 11 W |
| Tibetts Creek | Stream | | Jones | 42 14 03 N | 091 07 17 W |
| Tices Ferry (historical) | Locale | 186 | Muscatine | 41 32 17 N | 091 08 14 W |
| Tick Ridge School | School | 292 | Monroe | 40 56 34 N | 093 00 12 W |
| Tick Ridge Woods County Park | Park | 214 | Henry | 41 08 01 N | 091 40 31 W |
| Tick Ridge Woods Park | Park | 186 | Henry | 41 08 05 N | 091 42 16 W |
| Tickel Cemetery | Cemetery | 292 | Marion | 41 12 54 N | 093 17 25 W |
| Ticonic | Populated Place | 330 | Monona | 42 09 58 N | 095 57 09 W |
| Ticonic Post Office (historical) | Post Office | 328 | Monona | 42 09 13 N | 095 57 29 W |
| Tiernan Homestead Natural Area | Park | 364 | Pocahontas | 42 49 13 N | 094 35 59 W |
| Tieville (historical) | Locale | 320 | Monona | 42 01 35 N | 096 13 07 W |
| Tieville Bend | Bend | 316 | Monona | 42 01 15 N | 096 14 17 W |
| Tieville Post Office (historical) | Post Office | 325 | Monona | 42 05 60 N | 096 14 01 W |
| Tiffin | Locale | 210 | Johnson | 41 42 13 N | 091 39 51 W |
| Tiffin | Populated Place | 215 | Johnson | 41 42 21 N | 091 39 47 W |
| Tiffin East Bound Rest Area | Locale | 220 | Johnson | 41 41 37 N | 091 40 57 W |
| Tiffin Fire Department | Building | 216 | Johnson | 41 42 25 N | 091 39 46 W |
| Tiffin Post Office | Post Office | 218 | Johnson | 41 42 24 N | 091 39 51 W |
| Tiffin School Community Library | Building | 218 | Johnson | 41 42 23 N | 091 40 04 W |
| Tiffin West Bound Rest Area | Locale | 215 | Johnson | 41 41 42 N | 091 40 50 W |
| Tileville | Populated Place | 320 | Madison | 41 20 53 N | 093 56 10 W |
| Tilford Cemetery | Cemetery | 257 | Mahaska | 41 29 16 N | 092 31 57 W |
| Tilford Middle School | School | 241 | Benton | 42 09 31 N | 092 01 09 W |
| Tilton | Populated Place | 258 | Poweshiek | 41 30 35 N | 092 21 09 W |
| Tilton Cemetery | Cemetery | 227 | Jackson | 42 07 25 N | 090 40 47 W |
| Tilton Cemetery | Cemetery | 227 | Jackson | 42 07 50 N | 090 40 40 W |
| Tilton Evangelical Methodist Church | Church | 253 | Poweshiek | 41 30 35 N | 092 21 14 W |
| Tilton Post Office (historical) | Post Office | 276 | Poweshiek | 41 31 00 N | 092 24 11 W |
| Tilton Post Office (historical) | Post Office | 258 | Poweshiek | 41 30 35 N | 092 21 09 W |
| Tim Coffee Park | Park | 369 | Winnebago | 43 16 14 N | 093 38 09 W |
| Timber City Golf Course | Locale | 223 | Jackson | 42 02 58 N | 090 39 17 W |
| Timber Creek | Stream | | Harrison | 41 34 15 N | 095 50 51 W |
| Timber Creek | Stream | | Marshall | 42 01 44 N | 092 49 15 W |
| Timber Creek Cemetery | Cemetery | 303 | Marshall | 41 58 04 N | 092 54 37 W |
| Timber Creek Park | Park | 279 | Marshall | 42 01 10 N | 092 53 58 W |
| Timber Creek Post Office (historical) | Post Office | 303 | Marshall | 41 56 45 N | 092 53 04 W |
| Timber Lake | Reservoir | 225 | Johnson | 41 49 10 N | 091 40 23 W |
| Timber Ridge Campground | Locale | 374 | Adams | 41 02 55 N | 094 44 41 W |