High Quality Content by WIKIPEDIA articles! Azusa is a city in Los Angeles County, California, United States. The population was 46,361 at the 2010 census, up from 44,712 at the 2000 census. Though sometimes assumed to be a compaction of the phrase "everything from A to Z in the USA" from an old Jack Benny joke, the place name "Azusa" traces back to at least the 18th century. Azusa originally referred to the San Gabriel Valley and river, and likely derives from the Tongva place name Asuksagna.