PHYSICAL AND CLIMATIC SETTING 23 



is determined by the distance of the high ridge of 

 the Coast Bange from the ocean, narrow at the west, 

 increasing toward the central part, where the San 

 Gabriel and Santa Ana valleys extend northerly and 

 easterly sixty miles or more from Los Angeles to 

 the mesas and foothills of the high range on the east, 

 and then narrowing again to its southern limit just 

 below San Diego Bay. Owing to its environment and 

 exposure, as well as its latitude, this region has more 

 heat than the more northerly coast sections, though 

 in its extensions away from the ocean it has had, in 

 some places and at long intervals, a brief drop in 

 temperature to a degree as low as other valleys with 

 similar elevations. It is on the whole, however, most 

 equable in its temperature and by this widely known 

 characteristic has attracted settlement and develop- 

 ment in some respects beyond other districts of the 

 State. The products are large and various, includ- 

 ing most of the present output of citrus fruits and 

 walnuts, most of the beans, much of the sugar-beets 

 and truck crops for overland shipment, and dairy, 

 poultry, hay, grain,, and orchard fruits for a part of 

 its local consumption. It is for the most part an 

 irrigated district, though some crops are success- 

 fully grown along the coast by rainfall and on the 

 uplands away from the coast good results are at- 

 tained by dry-farming. The rainfall average varies 

 locally from 10 to 18 inches, part of which comes 

 from the Mexican storm system in summer and early 

 fall showers which are of little account except in 

 truck fields and flower-gardens, and occasionally in- 



