1850 Counties of Iowa
| County | Description | Area in sq miles | Courts held at | Pop in 1850 |
| Allomakee | northeast corner, crossed by Iowa river | blank | Lansing | 777 |
| Appanoose | on south side | blank | Centreville | 3,131 |
| Benton | on eastern side, crossed by Cedar river | 660 | Vinton | 672 |
| Black Hawk | NE part, crossed by Cedar & Black Hawk rivers | 625 | main town Cedar Falls | 135 |
| Boone | central part, crossed by Des Moines river | 600 | Booneville | 735 |
| Buchanan | eastern part, | blank | Independence | 517 |
| Cedar | eastern part, crossed by Cedar river | blank | Tipton | 3,941 |
| Clarke | southwest part | blank | blank | 79 |
| Clayton | northeast boundary, west side of Mississippi river | 720 | Gottenburgh | 4,053 |
| Clinton | eastern boundary, west side of Mississippi river, Wabesipinnica river on the south | 1012 | Camanche | 2,922 |
| Dallas | western part | blank | Adell | 854 |
| Davis | southern boundary, intersected by Des Moines river at northeast corner | blank | Bloomfield | 7,264 |
| Decatur | southern boundary | blank | blank | 965 |
| Delaware | eastern part | 576 | Delhi | 1,759 |
| Des Moines | southeast part, Mississippi river on east & Chickahoma river on southwest | 410 | Burlington | 12,987 |
| Du Buque | northeastern part, Mississippi river on northeast | blank | Du Buque | 10,841 |
| Fayette | north eastern part | blank | West Union | 825 |
| Fremont | southwest corner, Missouri river on west | blank | Dawsonburgh | 1,244 |
| Henry | south eastern part, crossed by Chicagua river | 432 | Mount Pleasant | 8,707 |
| Iowa | no description | blank | blank | 822 |
| Jackson | north eastern boundary on Mississippi river | 628 | Bellevue | 7,210 |
| Jasper | central part | blank | Newton | 1,280 |
| Jefferson | southeast part | 380 | Fairfield | 8,890 |
| Johnson | eastern part, crossed by Iowa river | 610 | Iowa City (Capital) | 4,472 |
| Jones | eastern part, crossed by Wapsipinecon river | 576 | Anamosa | 3,007 |
| Keokuk | southeast part | blank | Lancaster | 4,822 |
| Lee | southeast corner, Des Moines river on southwest, Mississippi river on southeast | 600 | Fort Madison | 18,860 |
| Linn | toward east part | 720 | Marion | 5,444 |
| Louisa | eastern boundary, crossed by Iowa river, with Mississippi river on east | 442 | Wapello | 4,939 |
| Lucas | southern part | blank | Chariton | 471 |
| Madison | southwest part | blank | blank | 1,179 |
| Mahaska | toward south part, crossed by Des Moines river | blank | Oskaloosa | 5,989 |
| Marion | central part, crossed by Des Moines river | blank | Knoxville | 5,482 |
| Marshall | central part, crossed by Iowa river | blank | blank | 338 |
| Monroe | southern part | blank | Albia | 2,884 |
| Muscatine | eastern boundary, Mississippi river on east | 440 | Muscatine | 5,731 |
| Page | south boundary | blank | Nodaway | 551 |
| Polk | central part, crossed by Des Moines river | blank | Des Moines | 4,515 |
| Pottawatamie | west boundary, Missouri river on west | blank | blank | 7,828 |
| Poweshiek | central part | blank | Montezuma | 615 |
| Scott | south eastern boundary, Mississippi river on southeast | 540 | Davenport | 5,986 |
| Van Buren | on south boundary, crossed by Des Moines river | 504 | Keosauque | 12,270 |
| Wapello | in southeastern part, crossed by Des Moines river | blank | Ottumwa | 8,471 |
| Warren | toward southern part | blank | Indianola | 961 |
| Washington | in southeastern part, Iowa river on northeast | 648 | Washington | 4,957 |
| Wayne | on south boundary | 375 | blank | 340 |
| Winneshiek | north boundary, crossed by Upper Iowa river | blank | Fort Atkinson | 546 |