List of California air districts

In 1947, the State of California enacted the Air Pollution Control Act that authorized the creation of Air Pollution Control Districts (APCD) or Air Quality Management Districts (AQMD) in every county of the State. California has 22 APCDs, 12 AQMDs and 1 Air Resources District for a total of 35 districts:
History.
The California Air Pollution Control District Act of 1947 allowed 1 or more counties to form air pollution districts. The California Bay Area Pollution Control Act of 1955 created the Bay Area Air Pollution Control District. The California Mulford-Carrell Air Resources Act of 1967 resulted in the creation of 11 air basins.