Active Prefixes in Area Code 820

- 820-999
- Oxnard, California
- 820-333
- Thousaoaks, California
- 820-666
- Snlusobspo, California
- 820-444
- Newburyprk, California
- 820-200
- Thousaoaks, California
- 820-400
- Parkfield, California
- 820-222
- Camarillo, California
- 820-777
- Santapaula, California
- 820-300
- Guadalupe, California
- 820-201
- Oxnard, California
- 820-888
- Simivalley, California