Azusa (Tongva: Asuksa-nga) is a city in the San Gabriel Valley region of Los Angeles County, California United States at the foot of the San Gabriel Mountains located east of downtown Los Angeles.
Its population was 50,000 in 2020, an increase from 46,361 at the 2010 census. Azusa is located along historic Route 66, which passes through the city on Foothill Boulevard and Alosta Avenue.
Azusa is bordered by the San Gabriel Mountains range to the north, Irwindale to the west, the unincorporated community of Vincent to the southwest, Glendora and the unincorporated community of Citrus to the east, and Covina to the south.
The place name Azusa dates to the Mexican Alta California era in the 19th century when Azusa was used to refer to the San Gabriel Valley and the San Gabriel River. It appears to have been derived from the Tongva place name Asuksa-nga.
The area was part of the homeland of the indigenous Tongva people (Gabrieleño Indians) since at least 55 BC. A backronym, "Azusa stands for everything from A to Z in the U.S.A.", has been a phrase used to promote the city by organisations such as the Chamber of Commerce for many years.
The first Mexican settlement in Azusa was at the Rancho el Susa in 1841, a Mexican land grant from the Alta California Governor Juan Bautista Alvarado to Luis Arenas. In 1844, Arenas sold the rancho's land to Henry Dalton, an English immigrant and wealthy merchant from the Pueblo of Los Angeles, for $7,000. He renamed it Rancho Azusa de Dalton, and had built a winery, distillery, vinegar house, meat smokehouse, and flour mill. Also, a vineyard was planted. Dalton built a house here on a place known as Dalton Hill, near 6th Street and Cerritos Avenue in Azusa.
Dalton was also the owner of the large, adjacent Rancho San Francisquito and Rancho Santa Anita properties. In the end, Dalton owned an unbroken expanse of land from present-day San Dimas to the eastern edge of Pasadena. A portion of Azusa west of the San Gabriel River was within adjacent Rancho Azusa de Duarte.