After the
attack on Pearl Harbor on December 7, 1941, it was feared that some Japanese Americans might be loyal to the
Empire of Japan and
Emperor of Japan. This was in spite of the fact that U.S. intelligence investigations, summarized in the report of Special Representative to the State Department Curtis B. Munson in November 1941, concluded that Japanese Americans posed no threat whatsoever to national security; that "There is no Japanese 'problem' on the Coast." Nevertheless, President
Franklin D. Roosevelt on February 19, 1942, signed
Executive Order 9066, which authorized the
Secretary of War to prescribe certain areas as military zones, clearing the way for the incarceration of
Japanese Americans,
German Americans, and
Italian Americans in U.S.
concentration camps. The Los Angeles County Fairgrounds was selected as one of the
Southern California detention camps. The other Los Angeles County camp selected was the
Santa Anita assembly center at the
Santa Anita Racetrack, which is also a California Historic Landmark (No. 934.07). A California Historic Landmark plaque is located near Fairplex, on the grassy drop off area, north of the intersection of Canyon Way and West McKinley Avenue, at around 1099 West McKinley Avenue, Pomona, California. Construction on the Pomona Assembly Center began on March 21, 1942, and the camp officially opened on May 7, 1942. The Pomona Facility consisted of 309 barracks, 8 mess halls, and 36 shower and latrine facilities. The first group of 72 Japanese American citizens arrived on May 9. By May 15, 1942, the Pomona site was operating near capacity, with 4,270 internees. Pomona reached a peak population of 5,434 before its closing on August 24, 1942. Most internees there were transferred to
Heart Mountain in Wyoming. The site remained in use for the duration of the war, first housing U.S. troops, and then German and Italian
prisoners of war. Today, the site serves as the Fairplex parking lot. In California, 13 temporary detention facilities were built. Large venues that could be sealed off were used, such as
fairgrounds,
horse racing tracks and
Works Progress Administration labor camps. These temporary detention facilities held Japanese Americans while permanent concentration camps were built in more isolated areas. In California
Camp Manzanar and
Camp Tulelake were built. Executive Order 9066 took effect on March 30, 1942. The order required all native-born Americans and long-time legal residents of Japanese ancestry living in California to surrender themselves for detention. In January 1945 the Supreme Court ruled in
ex parte Endo that it was illegal to detain loyal Japanese Americans without cause, and the camps were ordered closed. The last Japanese Americans were released in May 1946. In total 97,785 Californians of Japanese ancestry were held during the war. == Marker==