| Zip Code | City | Population ↓ |
|---|---|---|
| 63021 | Ballwin | 55,944 |
| 63129 | Saint Louis | 51,893 |
| 63031 | Florissant | 50,568 |
| 63123 | Saint Louis | 50,347 |
| 63017 | Chesterfield | 42,686 |
| 63136 | Saint Louis | 42,385 |
| 63122 | Saint Louis | 41,416 |
| 63033 | Florissant | 41,037 |
| 63011 | Ballwin | 36,515 |
| 63119 | Saint Louis | 34,732 |
| 63114 | Saint Louis | 34,341 |
| 63125 | Saint Louis | 32,750 |
| 63146 | Saint Louis | 31,348 |
| 63128 | Saint Louis | 30,168 |
| 63130 | Saint Louis | 28,978 |
| 63121 | Saint Louis | 24,126 |
| 63043 | Maryland Heights | 22,123 |
| 63141 | Saint Louis | 20,781 |
| 63137 | Saint Louis | 20,390 |
| 63135 | Saint Louis | 19,764 |
| 63005 | Chesterfield | 19,734 |
| 63034 | Florissant | 19,031 |
| 63105 | Saint Louis | 19,003 |
| 63138 | Saint Louis | 18,602 |
| 63131 | Saint Louis | 18,531 |
| 63042 | Hazelwood | 18,143 |
| 63025 | Eureka | 17,708 |
| 63074 | Saint Ann | 15,888 |
| 63126 | Saint Louis | 15,201 |
| 63134 | Saint Louis | 14,023 |
| 63132 | Saint Louis | 13,995 |
| 63124 | Saint Louis | 10,997 |
| 63044 | Bridgeton | 10,821 |
| 63117 | Saint Louis | 9,691 |
| 63143 | Saint Louis | 9,097 |
| 63144 | Saint Louis | 9,027 |
| 63040 | Wildwood | 8,662 |
| 63088 | Valley Park | 8,473 |
| 63038 | Wildwood | 7,153 |
| 63133 | Saint Louis | 6,763 |
| 63127 | Saint Louis | 5,235 |
| 63140 | Saint Louis | 291 |
| 63045 | Earth City | 0 |
The data shown reflect ZCTAs from the US Census. As of 2024, there are 43 ZCTAs in St. Louis County, Missouri (US Census).