| Minor Civil Division | 1910 | 1900 | 1890 |
| LOUISA COUNTY | 12,855 | 13,516 | 11,873 |
| Columbus City township, including Columbus City and Columbus Junction towns | 2,794 | 2,757 | 2,595 |
| Columbus City town | 375 | 388 | 459 |
| Columbus Junction town | 1,185 | 1,099 | 953 |
| Concord township | 620 | 828 | 700 |
| Elliot township, including Oakville town | 981 | 873 | 377 |
| Oakville town* | 389 | | |
| Elm Grove township | 496 | 576 | 596 |
| Grandview township, including Grandview and Letts towns | 1,522 | 1,397 | 1,262 |
| Grandview town* | 374 | | |
| Letts town | 435 | 387 | 325 |
| Jefferson township | 475 | 608 | 626 |
| Marshall township | 544 | 608 | 656 |
| Morning Sun township, including Morning Sun town | 1,591 | 1,761 | 1,617 |
| Morning Sun town | 897 | 948 | 881 |
| Oakland township | 462 | 562 | 447 |
| Port Louisa township | 608 | 653 | 611 |
| Union township | 529 | 546 | 541 |
| Wapello township, including Wapello city | 2,233 | 2,347 | 1,845 |
| Wapello city | 1,326 | 1,398 | 1,009 |
| | | | |
| * Incorporated in 1902 | | | |
