California during World War II was a major contributor to the World War II effort. California's long Pacific Ocean coastline provided the support needed for the Pacific War. California also supported the war in Europe. After the Japanese attack on Pearl Harbor on December 7, 1941, most of California's manufacturing was shifted to the war effort. California became a major ship builder and aircraft manufacturer. Existing military installations were enlarged and many new ones were built. California trained many of the troops before their oversea deployment. Over 800,000 Californians served in the United States Armed Forces. California agriculture, ranches and farms were used to feed the troops around the world. California's long coastline also put the state in fear, as an attack on California seemed likely. California was used for the temporary and permanent internment camps for Japanese Americans. The population grew significantly, largely due to servicemen who were stationed at the new military bases/training facilities and the mass influx of workers from around the U.S. in the growing defense industries. With all the new economy activity, California was lifted out of the Great Depression. Over 500,000 people moved to California from other states to work in the growing economy. California expanded its oil and mineral production to keep up with the war demand.
 A total of 12% of all U.S. Government war contracts were awarded to California companies. A total of 17% of the war materials were made in California. Mining, natural gas, and oil production were active industries in California before World War II, and these rapidly expanded to support the war effort. Like World War I, the mines and mining towns came to life again, due to an increase in demand for gold, copper, and silver. California oil production doubled, the synthetic rubber industry created in California and California agricultural output almost tripled. In 1941 California oil production was 230,263,000 barrels; by the end of the war in 1945 the output was 326,555,000 barrels. Raw material was also shipped to California from Lend lease U.S. Allies. After the attack on Pearl Harbor and America entered the war, there was a quick build of new military bases, airfields, training camps, and other military installations. New military construction projects and the emerging war industries in California brought in tens of thousands of workers from across America. After the war, many stayed in California, with some others returning to their home states. Towns and cities next to military and industrial facilities grew and had an increase in the economy. California's population in 1940 was 6,907,387 and by 1950 it had grown to 10,586,223, a 53.3% increase. California received one eighth of all war orders. With the manpower shortage many women entered the workforce in manufacturing and other jobs held by men in the past. As factories added more shifts, a variety of stores and services increase operating hours. To retain workers, some businesses increased their employee benefits. Many military personnel who were trained in California returned after the war to tour the state, so California's tourist industries began to grow.
 California's mild climate made it ideal for year-round food production. With many men overseas, there was labor shortage at harvest time. The need for extra workers at harvest brought in  housewives and students. Some businesses even loaned workers to help with harvest and food packing as needed. The Woman's Land Army of America was one of the organizations helping in food production. Even with the increase in food production there was mandatory food rationing. Civilians were encouraged to plant Victory gardens to help with the food shortage. The slogan "grow your own, can your own", was started at start of the war and referred to families growing and canning their own food in victory gardens. With its mild climate most victory gardens were grown almost year-round. Tires and gasoline were also rationed.
Rationing of wool fabric was also required during the war. This is one of the causes of the June 1943 Zoot Suit Riots in Los Angeles.
 
 California was a major supplier of ammunition for the war.  Riverbank Army Ammunition Plant in Stanislaus County and Benicia Arsenal were two of the largest ammunition makers. In San Bernardino the Western Stove Company built incendiary bombs. 
 The largest World War II accident in California was the Port Chicago disaster. The Liberty ship SS E. A. Bryan exploded on July 17, 1944, while being loaded with ammunition. About 4,600 tons (4,173 tonnes) of explosives had been loaded in the ship's holds at the time. The explosion killed 320 sailors and civilians and injured 390 others. 
 Hollywood's motion-picture industry continued to make movies during the war. In addition to entertainment films, Hollywood made training films and films to raise morale. The 1942 film The Arm Behind the Army showed how important home support of the war was.
 Bob Hope volunteered with the United Service Organizations (USO) and entertained troops during World War II and for decades later (1941 to 1991). Hope brought many Hollywood stars with him on his USO tours.  
 Desi Arnaz was stationed at Birmingham General Army Hospital in Van Nuys, California  during the war to entertain the troops there. Arnaz had a bad knee and so was transferred to the US Army Medical Corps. Arnaz also coordinated with the stars that visited the hospital. 
 Disney famously dedicated a large portion of their business to making propaganda films.
 To help pay for the war the U.S. sold war bonds. With its booming economy during World War II, Californians was one of the top of U.S. War Bonds sold. Much of the advertising for war bonds was donated. The spirit of sacrifice was never stronger for the defense of democracy and a way of honoring the sacrifices of American troops.  Named after the 1942 Hollywood Victory Caravan, Paramount-produced film promoted bond sales in a 1945, post War. The short film included Bing Crosby, Bob Hope, Alan Ladd, William Demarest, Franlin Pangborn, Barbara Stanwyck, Humphrey Bogart, and others. Other heroes like boxing Joe Louis and Joe DiMaggio sold war bonds. Albert Einstein donated the original copies of his manuscript on the theory of relativity for auction to raise money for war bonds.
 California National Guard was mobilized and called to active duty in August 1940. The US Army recruited the first group to deploy to the war in Europe. The others troops called up were sent to the Pacific war. Between 1940 and 1941 about 12,000 California National Guard troops were called up to service in federal duty. Some troops were used for the defense of California and Hawaii. California National Guard was used for coast patrols, security guards for the Army Air Force bases, railroad bridges, rail tunnels and major dams. Major training bases are Camp Roberts and Camp San Luis Obispo.
 Due to the attack on Pearl Harbor and on California civil defense systems were started in California. Office of Civilian Defense was founded on  May 20, 1941, and the Office of Civil Defense in May 1941. The Civil Air Patrol was started on December 1, 1941, in which civilian planes and spotters were used in air reconnaissance, search-and-rescue, and transport. After the attacks on California the Coast Guard Auxiliary, became very active in the use of civilian boats and crews for reconnaissance and search-and-rescue. Towers were built along coastal California, staffed with spotters to look for enemy aircraft working with the Ground Observer Corps. In February 1942 the Federal government started War Time, ending in September 1945. With War Time California time was renamed to Pacific War Time with special Daylight Savings times. The Women Airforce Service Pilots (WASP) started on August 5, 1943, used 1,074 civilian women pilots to fly new warplanes from the factories to Army airfields for training and deployment points. WASP pilots also towed targets for live anti-aircraft artillery practice, towed gliders for practice landings, simulated strafing missions, and transported cargo. WASP California headquarters was at Santa Ana Army Air Base, Merced Army Airfield, Minter Field, and Victorville Army Airfield
 American railroads moved 70% of all freight transported in the United States in 1940. During World War II the passenger and freight volume increased vastly. Railroads moved about 90% of the military's cargo need and transported 98% of military personnel. Railroads worked overtime to keep up with demand. It was patriotic to avoid all unnecessary travel, to give space needed for troop movement. Railroad brought troops to California training centers and camps. Railroad brought workers to California's growing defense industry. During World War II rail-line moved to Diesel locomotives and away from the labor-intensive steam locomotives.  The Army had special hospital cars built to move wounded soldiers, one operated out of San Francisco.
 The development of new systems was a key to winning the war. World War 2 brought about many new technologies. Some California colleges and universities joined in the V-12 Navy College Training Program training volunteers for Navy commission. Some California universities also had classes for aeronautical engineering, resident inspectors of ordinance and naval material, and a liaison for the National Defense Research Committee.
 After the war Operation Magic Carpet started to bring the troops home, some brought home war brides. On October 30, 1944, Governor Earl Warren started the California Veteran's Commission. The Commission worked to help veterans re-entry into civilian life. The Commission working with United States Department of Veterans Affairs, California Military Department, state agencies, local governments, and community groups like: American Legion, Veterans of Foreign Wars, and Disabled American Veterans. Many Veterans Health Administration facilities were opened in the state. Veteran's Bond Act of 1943 helped veterans to purchase a home or farm. Veterans started families, that is called the baby boom, birth rates increased in the U.S. and California.
 California became a major builder of ships for the war. Under the Emergency Shipbuilding program, cargo ships like Liberty ships and Victory ships were built in days, not the normal months. Ships that could be repaired overseas greatly reduced repair time, so California shipyards also built floating dry docks like the Large Auxiliary Floating Dry Docks and Medium Auxiliary Floating Dry Docks. As fear of an attack on California seemed likely, the War Department requested some ships be built at an inland ports, so many new ships were built at the Port of Stockton, seventy nautical miles from the ocean. Henry J. Kaiser built day care centers at his shipyards in Richmond. Kaiser Steel was headquartered in Fontana, California. Some of the ships were given to the Allies of World War II through the Lend-Lease act of March 11, 1941. At the end of the war there was a surplus of ships and most shipyards were closed. Surplus ships were either sold or put into the Navy Reserve Fleet, like the Suisun Bay Reserve Fleet. California ship yards:
 Major
 Minor
 Major
 Minor
 Built in California during World War 2 were: B-17 Flying Fortress, Lockheed P-38 Lightning, Douglas C-47 Skytrain, Douglas SBD Dauntless, Douglas A-26 Invader, Lockheed Ventura, Lockheed Model 18 Lodestar, Lockheed P-2 Neptune, Lockheed Constellation, Douglas P-70 Nighthawk, Douglas DC-5, Douglas C-54 Skymaster, Douglas BTD Destroyer, Douglas A-33, Douglas TBD Devastator, Consolidated PB4Y-2 Privateer, Northrop A-17, Northrop BT, Northrop N-3PB, Northrop P-61 Black Widow, McDonnell FH Phantom, Consolidated B-24 Liberator, Consolidated PB2Y Coronado, Consolidated TBY Sea Wolf, Consolidated B-32 Dominator, Consolidated P-30, North American B-25 Mitchell, North American P-51 Mustang, Vultee A-31 Vengeance, Vultee BT-13 Valiant, Vultee P-66 Vanguard, Vultee V-11, Interstate Cadet, North American T-6 Texan, Douglas A-20 Havoc, Lockheed C-69 Constellation, Consolidated PBY Catalina, Interstate TDR, Timm N2T Tutor, Ryan PT-22 Recruit, Ryan ST and the Waco CG-4 / Timm CG-4A . The Lockheed Hudson built in Burbank was delivered to Canada and then the United Kingdom starting in 1939. By the end of the war California had 70% of the aerospace manufacturing in the United States and had built over 200,000 planes. Hughes H-4 Hercules, Victory Trainer and Bartlett Zephyr were built in California, but not used.  The California Institute of Technology in Pasadena, California started a School of Aeronautics and other aeronautic research labs in the early 1920s, this helped California become a major aerospace manufacturing center.

Aircraft manufacturers of World War II in California:
 During World War II all California civilian automobile manufacturing ended.
 Joshua Hendy Iron Works was the biggest supplier of reciprocating engines for Liberty ships in the country. It was also the
only manufacturer of large steam turbine propulsion systems on the West Coast.
 Like other states in the desert Southwest, many of the new military installations built were United States Army airbases. California's weather, wide open spaces, railroad connections, and access to ocean made it an ideal location for training pilots, also armored vehicles operators.
 The largest United States Army training installation in the history of the United States was the Desert Training Center. To prepare troops for the battles in the North African campaign, the army had General Patton build many desert training camps in Southern California and a few in Arizona. The camps were built in the Mojave Desert and Sonoran Desert. The open space let the Army and Army Air Corps use live fire to train troops, test and develop equipment. Tactical doctrines, techniques, and training methods for combat were developed from this training. From 1 April 1942 to 1 July 1944, the complete training area covered 18,000 square miles. The camp reached from Pomona, California east to almost to Phoenix, Arizona and from Yuma, Arizona northward into the southern tip of Nevada.
 California Army Divisional Camps
 California Army Depots
 California Army Airfields
 Desert Training Center California Hospitals
 For World War 2 existing California Army bases were enlarged and many new bases were built. Bases were used for induction, training, deployment, supply depots, hospitals and housing of POWs.
 Existing United States Army Air Corps air bases were enlarged to house and train the many new crews needed. Almost all civilian airports and airstrips were converted to Army Air training centers. Almost all civilian air flights were cancelled. Many new airstrips and landing pads were built for pilot landing and take-off training. Air bases had housing and meals for the troops. Some airstrips and landing pads had no support buildings, as they were used only for landing and take-off training.
United States Army Air Corps World War II bases, airstrips and landing pads in California:
 United States Navy's main marine bases were located in the deepwater ports of: San Diego Bay, Port of Los Angeles, San Francisco Bay and the Stockton Deepwater Shipping Channel. The US Navy during WW2 Pacific Fleet operated: ports, supply depots and airfields for aircraft carrier training, also blimps used for patrol of the coast. Post World War II many shipyards became home of the Pacific Reserve Fleet used to store the many surplus ships.
United States Navy World War II bases and stations in California:
 Camp Pendleton became the main training grounds for training Marines including landing craft school, amphibious tractor school, beach battalion school, amphibious communications school, and a medical field service school. Skills that would be used across the island hopping in the Pacific War and the war in Europe.
 In times of war, like during World War II, the United States Coast Guard operated as a branch of the Department of the Navy. In California the Coast Guard operated out of the 12th Naval District. Coast Guard's World War 2 Navy support included use of Coast Guard cutters, patrol boats, bases, stations and lighthouses. Patrols and search and rescue missions being the main task.
 United States Coast Guard World War II bases in California:
 The United States Merchant Marine operated merchant ships out of California US Navy and private ports to supply goods needed around the world. Most merchant ships operated with civilian merchants and US Navy armed guards to man the deck guns under the Merchant Marine Act of 1936. Merchant Marine operated many different types of ships, the most numerous type was the Liberty ships and Victory ships. Merchant Marine training was conducted by the Coast Guard.
The Maritime Service established several Merchant Marine training centers in California for World War 2: