| 1890 | 1900 | 1910 | 1920 | 1930 | 1940 | 1950 | |
| JC total | 23131 | 24817 | 25914 | 26462 | 30276 | 33191 | 45756 |
| IC total | 7173 | 7987 | 10091 | 11267 | 15340 | 17182 | 27122 |
| JC nonwhite | 58 | 62 | 65 | 68 | 112 | 89 | 201 |
| IC nonwhite | 50 | 62 | 57 | 60 | 110 | 77 | 169 |
Source: US Census of Population. JC=Johnson County; IC=Iowa City. “Nonwhite” used to capture changing census definitions and categories across these years.