The first phase of the mass incarceration of 97,785 Californians of Japanese ancestry during the war. Most internees were U.S. citizens. Pursuant to Executive Order 9066, signed by President Franklin D. Roosevelt on February 19, 1942, fifteen makeshift detention facilities were constructed at various California racetracks, fairgrounds and labor camps. These facilities confined Japanese American citizens until permanent location centers such as those in Manzanar and Tule Lake in California could be built in more isolated areas of the country. Beginning on March 30, 1942, native-born American citizens and long-time legal residents of Japanese ancestry living in California were ordered to surrender themselves for detention. 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. On August 24, 2016 a plaque was erected to recognize the former assembly center, POW camp. Location It is located at 1101 W. McKinley Ave., Pomona, California, approximately east of downtown Los Angeles. Transportation The facility features a Metrolink platform on the north side of the property, where San Bernardino Line trains provide passenger services on fair days. Los Angeles County operates a free Park and Ride facility for commuters adjacent to the grounds at 1810 Gillette Road with 553 spaces available. Weekday connections to/from downtown Los Angeles are available via the Foothill Transit route 699 bus. The Foothill Transit route 197 bus connects the facility to the Montclair Station and the Pomona Station. In popular culture The rodeo scenes in Pee-wee's Big Adventure were shot at the Fairplex in 1985. 2 songs: The Loco-Motion & The little Red Caboose from the 1994 Kidsongs video: "Boppin' with the Biggles" were shot at the Railroad museum where 3 locomotives on the Union Pacific Railroad : 4–12–2 #9000, Centennial Built Diesel 6915, & Big Boy 4014, Are Cameoed throughout