Identifiers: city · CDP
| Rank | Community | Population |
|---|---|---|
| 1 | Concord (city), CA | 125,410 |
| 2 | Antioch (city), CA | 115,291 |
| 3 | Pittsburg (city), CA | 76,416 |
| 4 | Brentwood (city), CA | 64,292 |
| 5 | Oakley (city), CA | 43,357 |
| 6 | Martinez (city), CA | 37,287 |
| 7 | Pleasant Hill (city), CA | 34,613 |
| 8 | Mountain House (city), CA | 24,499 |
| 9 | Bay Point (CDP), CA | 23,896 |
| 10 | Discovery Bay (CDP), CA | 15,358 |
| 11 | Clayton (city), CA | 11,070 |
| 12 | Rio Vista (city), CA | 10,005 |
| 13 | Contra Costa Centre (CDP), CA | 6,808 |
| 14 | Vine Hill (CDP), CA | 4,323 |
| 15 | Pacheco (CDP), CA | 4,183 |
| 16 | Mountain View (CDP), CA | 2,622 |
| 17 | Bethel Island (CDP), CA | 2,131 |
| 18 | Knightsen (CDP), CA | 1,596 |
| 19 | Byron (CDP), CA | 1,140 |
| 20 | Isleton (city), CA | 794 |