Feature Name | Class | Elev. meters | County | Latitude DMS | Longitude DMS |
| Clark Cemetery | Cemetery | 198 | Washington | 41 25 50 N | 091 29 31 W |
| Clark Creek | Stream | | Allamakee | 43 25 49 N | 091 21 48 W |
| Clark Elementary School | School | 231 | Henry | 40 55 22 N | 091 24 11 W |
| Clark Elementary School | School | 372 | Plymouth | 42 47 45 N | 096 10 11 W |
| Clark Eye Center | Hospital | 333 | Wayne | 40 45 30 N | 093 19 08 W |
| Clark Field | Park | 225 | Linn | 41 59 28 N | 091 39 29 W |
| Clark Field House | Locale | 214 | Des Moines | 40 47 58 N | 091 07 49 W |
| Clark Fieldhouse | Park | 177 | Des Moines | 40 48 34 N | 091 06 39 W |
| Clark Hall | Building | 322 | Pottawattamie | 41 16 26 N | 095 48 01 W |
| Clark Lake | Reservoir | 368 | Cerro Gordo | 43 06 05 N | 093 11 06 W |
| Clark Memorial Tower | Tower | 318 | Madison | 41 19 12 N | 094 00 14 W |
| Clark Museum of Area History | Building | 437 | Dickinson | 43 20 08 N | 095 09 45 W |
| Clark Park | Park | 354 | Fayette | 42 57 34 N | 091 48 12 W |
| Clark Post Office (historical) | Post Office | 308 | Mills | 40 57 02 N | 095 32 25 W |
| Clark Racquet Center | Building | 225 | Linn | 41 59 25 N | 091 39 26 W |
| Clark Residence Hall | Building | 311 | Poweshiek | 41 45 03 N | 092 43 19 W |
| Clark School | School | 371 | Plymouth | 42 47 46 N | 096 10 15 W |
| Clark School | School | 350 | Woodbury | 42 32 39 N | 096 24 30 W |
| Clark-Allen Cemetery | Cemetery | 327 | Ringgold | 40 34 23 N | 094 20 43 W |
| Clarkdale | Locale | 282 | Appanoose | 40 46 55 N | 092 54 24 W |
| Clarkdale | Populated Place | 290 | Appanoose | 40 47 07 N | 092 54 18 W |
| Clarkdale Post Office (historical) | Post Office | 290 | Appanoose | 40 47 07 N | 092 54 18 W |
| Clarke Cemetery | Cemetery | 284 | Clarke | 40 58 40 N | 093 37 21 W |
| Clarke Cemetery | Cemetery | 214 | Louisa | 41 24 56 N | 091 28 58 W |
| Clarke College | School | 256 | Dubuque | 42 30 34 N | 090 41 26 W |
| Clarke Community Elementary School | School | 341 | Clarke | 41 01 58 N | 093 45 34 W |
| Clarke Community Schools | School | 344 | Clarke | 41 02 39 N | 093 46 15 W |
| Clarke County | Civil | 333 | Clarke | 41 02 00 N | 093 47 01 W |
| Clarke County Courthouse | Building | 350 | Clarke | 41 02 03 N | 093 46 01 W |
| Clarke County Historical Museum | Building | 326 | Clarke | 41 01 27 N | 093 45 57 W |
| Clarke County Hospital | Hospital | 344 | Clarke | 41 01 34 N | 093 46 07 W |
| Clarke County Sheriffs Office | Building | 350 | Clarke | 41 02 03 N | 093 46 01 W |
| Clarks Branch | Stream | | Cass | 41 10 12 N | 095 10 24 W |
| Clarks Ferry Recreation Area | Park | 170 | Muscatine | 41 27 30 N | 090 48 36 W |
| Clarks Ferry Recreation Area | Park | 169 | Scott | 41 27 28 N | 090 48 35 W |
| Clarks Lake | Reservoir | 269 | Jasper | 41 40 40 N | 093 20 48 W |
| Clarks Woods Park | Park | 376 | Winnebago | 43 15 39 N | 093 37 42 W |
| Clarkson (historical) | Locale | 233 | Warren | 41 30 02 N | 093 27 04 W |
| Clarkson (historical) | Populated Place | 284 | Warren | 41 20 04 N | 093 27 09 W |
| Clarkson Post Office (historical) | Post Office | 233 | Warren | 41 30 02 N | 093 27 04 W |
| Clarkson School | School | 249 | Polk | 41 37 22 N | 093 37 31 W |
| Clarksville | Locale | 285 | Butler | 42 46 48 N | 092 39 57 W |
| Clarksville | Populated Place | 287 | Butler | 42 47 05 N | 092 40 04 W |
| Clarksville City Hall | Building | 287 | Butler | 42 47 06 N | 092 40 06 W |
| Clarksville Community Nursing Home | Hospital | 286 | Butler | 42 47 06 N | 092 40 23 W |
| Clarksville Fire Department | Building | 287 | Butler | 42 47 05 N | 092 40 04 W |
| Clarksville Police Department | Building | 287 | Butler | 42 47 05 N | 092 40 04 W |
| Clarksville Post Office | Post Office | 287 | Butler | 42 47 01 N | 092 40 06 W |
| Clarksville Public Library | Building | 287 | Butler | 42 47 05 N | 092 40 04 W |
| Clarksville School | School | 286 | Butler | 42 47 14 N | 092 39 56 W |
| Clarmond Country Club | Locale | 379 | Wright | 42 44 30 N | 093 40 31 W |
| Classroom Annex | Building | 265 | Polk | 41 37 15 N | 093 36 16 W |
| Clausen City Park | Park | 352 | Mitchell | 43 22 48 N | 092 55 25 W |
| Clay | Locale | 229 | Washington | 41 10 39 N | 091 55 37 W |
| Clay Castle Museum | Building | 309 | Boone | 41 52 34 N | 093 49 16 W |
| Clay Cemetery | Cemetery | 256 | Jones | 42 10 20 N | 090 58 49 W |
| Clay Cemetery | Cemetery | 223 | Washington | 41 11 09 N | 091 55 20 W |
| Clay Center Cemetery | Cemetery | 342 | Hardin | 42 25 60 N | 093 03 01 W |
| Clay Center School | School | 333 | Wayne | 40 46 06 N | 093 29 51 W |
| Clay Central - Everly High School | School | 414 | Clay | 43 09 31 N | 095 19 23 W |
| Clay Central Community School | School | 431 | Clay | 43 03 45 N | 095 17 11 W |
| Clay County | Civil | 415 | Clay | 43 05 00 N | 095 09 01 W |
| Clay County Courthouse | Building | 402 | Clay | 43 08 31 N | 095 08 54 W |
| Clay County Fairground | Locale | 403 | Clay | 43 09 15 N | 095 09 11 W |
| Clay County Law Library | Building | 402 | Clay | 43 08 30 N | 095 08 53 W |
| Clay County Sheriffs Office | Building | 400 | Clay | 43 08 31 N | 095 08 45 W |
| Clay Grove Cemetery | Cemetery | 212 | Lee | 40 44 34 N | 091 33 56 W |
| Clay Mills | Populated Place | 223 | Jones | 42 11 03 N | 090 56 36 W |
| Clay Mills Post Office (historical) | Post Office | 223 | Jones | 42 11 03 N | 090 56 36 W |
| Clay Post Office (historical) | Post Office | 211 | Washington | 41 07 56 N | 091 55 44 W |
| Clay Street Park | Park | 268 | Black Hawk | 42 31 28 N | 092 26 52 W |
| Clay Township Cemetery | Cemetery | 408 | Shelby | 41 33 50 N | 095 05 20 W |
| Clay-Grove Church | Church | 211 | Lee | 40 44 34 N | 091 33 54 W |
| Clay's Grove Post Office (historical) | Post Office | 212 | Lee | 40 44 40 N | 091 33 54 W |
| Claybanks Forest | Forest | 325 | Cerro Gordo | 43 05 35 N | 093 03 49 W |
| Clayford (historical) | Locale | 235 | Jones | 42 12 00 N | 090 59 59 W |
| Clayford Post Office (historical) | Post Office | 228 | Jones | 42 11 26 N | 090 59 46 W |
| Claypool Cemetery | Cemetery | 354 | Union | 41 00 42 N | 094 01 37 W |
| Claypoole Cemetery | Cemetery | 198 | Lee | 40 41 02 N | 091 15 22 W |
| Clayton | Locale | 194 | Clayton | 42 54 14 N | 091 08 50 W |
| Clayton | Populated Place | 194 | Clayton | 42 54 14 N | 091 08 50 W |
| Clayton Cemetery | Cemetery | 277 | Buchanan | 42 19 60 N | 091 54 01 W |
| Clayton Cemetery | Cemetery | 330 | Clayton | 42 54 16 N | 091 09 51 W |
| Clayton Cemetery | Cemetery | 304 | Dallas | 41 31 03 N | 093 55 31 W |
| Clayton Center | Populated Place | 299 | Clayton | 42 53 00 N | 091 19 36 W |
| Clayton Center Cemetery | Cemetery | 314 | Clayton | 42 53 03 N | 091 19 21 W |
| Clayton County | Civil | 273 | Clayton | 42 50 00 N | 091 22 00 W |
| Clayton County Courthouse | Building | 227 | Clayton | 42 51 20 N | 091 24 12 W |
| Clayton County Fairgrounds | Locale | 270 | Clayton | 42 46 52 N | 091 17 07 W |
| Clayton County Farm | Building | 301 | Clayton | 42 53 28 N | 091 21 07 W |
| Clayton County Office Building | Building | 236 | Clayton | 42 51 40 N | 091 24 24 W |
| Clayton County Sheriffs Office | Building | 243 | Clayton | 42 51 25 N | 091 23 52 W |
| Clayton Post Office (historical) | Post Office | 194 | Clayton | 42 54 14 N | 091 08 50 W |
| Clear Cemetery | Cemetery | 291 | Lucas | 41 09 32 N | 093 08 42 W |
| Clear Creek | Stream | | Allamakee | 43 21 35 N | 091 12 47 W |
| Clear Creek | Stream | | Allamakee | 43 26 01 N | 091 24 31 W |
| Clear Creek | Stream | | Allamakee | 43 21 34 N | 091 12 45 W |
| Clear Creek | Stream | | Cerro Gordo | 43 08 24 N | 093 19 17 W |
| Clear Creek | Stream | | Jasper | 41 45 54 N | 093 15 51 W |
| Clear Creek | Stream | | Johnson | 41 40 12 N | 091 33 47 W |
| Clear Creek | Stream | | Keokuk | 41 15 15 N | 091 59 51 W |
| Clear Creek | Stream | | Linn | 41 50 56 N | 091 23 25 W |
| Clear Creek | Stream | | Story | 42 02 10 N | 093 38 56 W |
| Clear Creek Elementary School | School | 375 | Cerro Gordo | 43 07 46 N | 093 22 18 W |
| Clear Creek Elementary School | School | 238 | Johnson | 41 43 30 N | 091 47 34 W |
| Clear Creek High School | School | 218 | Johnson | 41 42 23 N | 091 40 04 W |
| Clear Creek Mobile Home Park | Populated Place | 207 | Johnson | 41 42 10 N | 091 39 51 W |
| Clear Creek Park | Park | 192 | Allamakee | 43 21 35 N | 091 12 55 W |
| Clear Creek Post Office (historical) | Post Office | 207 | Allamakee | 43 26 20 N | 091 25 13 W |
| Clear Creek School | School | 247 | Monroe | 41 08 56 N | 093 02 22 W |