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:Amador County APCD Antelope Valley AQMD Bay Area AQMD Butte County AQMD Calaveras County APCD Colusa County APCD Eastern Kern APCD El Dorado County AQMD Feather River AQMD Glenn County APCD Great Basin Unified APCD Imperial County APCD Lake County AQMD Lassen County APCD Mariposa County APCD Mendocino County AQMD Modoc County APCD Mojave Desert AQMD Monterey Bay Air Resources District North Coast Unified AQMD Northern Sierra AQMD Northern Sonoma County APCD Placer County APCD Sacramento Metropolitan AQMD San Diego County APCD San Joaquin Valley APCD San Luis Obispo County APCD Santa Barbara County APCD Shasta County AQMD Siskiyou County APCD South Coast AQMD Tehama County APCD Tuolumne County APCD Ventura County APCD Yolo-Solano AQMD