High Quality Content by WIKIPEDIA articles! The San Gabriel Valley is one of the principal valleys of southern California, United States. It lies to the east of the city of Los Angeles, to the north of the Puente Hills, to the south of the San Gabriel Mountains, and west of the Inland Empire. It derives its name from the San Gabriel River that flows southward through the center of the valley. At one time predominantly agricultural, the San Gabriel Valley is today almost entirely developed (largely in suburban form, but with certain areas beginning to urbanize) and is an integral part of the Greater Los Angeles metropolitan area. Pasadena is the largest city in the valley and is considered its urban hub.