The 15th Assembly District is entirely made up of Contra Costa County and covers over half of the County. 32% percent of its residents are Hispanic or Latino, nearly 15% are Asian and 10% are Black or African American. Assembly District 15 encompasses the following cities.

1. Antioch
2. Bay Point
3. Brentwood
4. Clayton
5. Concord
6. Clyde
7. Crocket
8. Martinez (Mountain View, Alhambra Valley, Reliz Valley, Vine Hill)
9. Pittsburg
10. Pleasant Hill
11. Pacheco
12. Port Costa
13. Walnut Creek – 0.5%