The core grouping of buildings within the concentration camps administered by both the War Relocation Authority (WRA) and the Wartime Civil Control Administration (WCCA). The large numbers of military style barracks built and administered by the WRA and the WCCA to provide shelter for thousands of individuals and families incarcerated in the camps in a small confined area required some method of organization for basic services such as the preparation and distribution of food, sanitation, etc. Buildings were situated into groupings called blocks. In most of the WRA camps, each residential block consisted of twelve to fourteen barracks along with a mess hall, communal bathroom and laundry facilities, and a recreation building. Each block typically housed between 250 and 300 people. 
Blocks in the WRA camps became a core unit of identification within the camp for many inmates. This was due in part to the fact that block populations often consisted of people who came from the same prewar geographical area or at least the same "assembly center." There were also blocks which were intentionally populated with particular groups of people, such as Issei bachelors or hospital workers, that gave them a particular character. Some blocks also became known for such things as having good food in the mess hall or as the site of beautiful gardens or organized gambling. 
Blocks and barracks were numbered and each "apartment" within a barracks building was assigned a letter. Thus, each individual "apartment" had a unique address consisting of the block number, barracks number, and unit letter. For example 12-1-A —the title of a postwar play by Wakako Yamauchi named after her family's address in Poston—refers to block 12, barracks 1, unit A. While blocks in most camps were numbered, blocks in Amache were designated by a number and letter, e.g. 6E. 
In addition to residential blocks, there were also administration blocks for staff offices and housing, storage, and other purposes.
Though blocks were also used in the WCCA camps (e.g. " assembly centers "), they were less regular, since the WCCA used existing facilities to set up these camps. In addition to having blocks of non-uniform size and layout, assembly centers sometimes used existing mess halls that fed multiple blocks.
In the WRA camps, appointed block managers served as go-betweens between the block and administration. In some cases, there were also inmate organized block councils that included representatives from the various barracks within a block.
Though there has been some study of the dynamics of block composition and block level camp politics, much remains to be written on this general topic. 
Block/barracks summary for each WRA camp:
|Concentration Camp||No. of Blocks||No. of Barracks|
|Amache||29 residential blocks||12 barracks per block|
|Gila River||53 total blocks (36 in Butte and 17 in Canal)||14 barracks per block|
|Heart Mountain||20 residential blocks||24 barracks in most blocks|
|Jerome||36 residential blocks||12 barracks per block|
|Manzanar||36 residential blocks||14 barracks per block|
|Minidoka||35 residential blocks||12 barracks per block|
|Poston||72 residential blocks (36 in Camp I, 18 each in Camps II and III)||14 barracks per block|
|Rohwer||36 residential blocks||12 barracks per block|
|Topaz||34 residential blocks||12 barracks per block|
|Tule Lake||40 residential blocks prior to segregation (26 more blocks added later, 10 of those after segregation, for a total of 66)||13 barracks per block|
For More Information
Burton, Jeffery F., Mary M. Farrell, Florence B. Lord, and Richard W. Lord. Confinement and Ethnicity: An Overview of World War II Japanese American Relocation Sites . Western Archeological and Conservation Center, National Park Service, 1999, 2000. Foreword by Tetsuden Kashima. Seattle: University of Washington Press, 2002. The 2000 version accessible online at http://www.nps.gov/parkhistory/online_books/anthropology74/ .
Hansen, Arthur A. "Cultural Politics in the Gila River Relocation Center, 1942-1943." Arizona and the West 27 (Winter 1985): 327-62.
Hayashi, Brian Masaru. Democratizing the Enemy: The Japanese American Internment . Princeton: Princeton University Press, 2004.
Nishimoto, Richard. Inside An American Concentration Camp: Japanese American Resistance at Poston, Arizona . Ed. Lane Ryo Hirabayashi. Tucson: University of Arizona Press, 1995.
Provinse, John H., and Solon T. Kimball. "Building New Communities during War Time." American Sociological Review 11.4 (Aug. 1946): 396–409.
Spicer, Edward H., Asael T. Hansen, Katharine Luomala, and Marvin K. Opler. Impounded People: Japanese Americans in the Relocation Centers . Washington, DC: U.S. Department of Interior, U.S. Government Printing Office, 1946. Tucson: University of Arizona Press, 1969.
- Most blocks at Heart Mountain included twenty-four residential barracks, twice as many as blocks in most other camps. Jeff Burton, et al., Confinement and Ethnicity: An Overview of World War II Japanese American Relocation Sites (Western Archeological and Conservation Center, National Park Service, 1999, 2000), accessed on March 21, 2014 at http://www.nps.gov/parkhistory/online_books/anthropology74/ce6a.htm .
- John H. Provinse, and Solon T. Kimball, "Building New Communities during War Time," American Sociological Review 11.4 (Aug. 1946), 405–06; Allen Hendershott Eaton, Beauty Behind Barbed Wire: The Arts of the Japanese in Our War Relocation Camps (New York: Harper, 1952), 50–51, 92–95; Richard Nishimoto, Inside An American Concentration Camp: Japanese American Resistance at Poston, Arizona . Edited by Lane Ryo Hirabayashi (Tucson: University of Arizona Press, 1995), 140; Charles Kikuchi Diary, Oct. 29, 1942, 1031, The Japanese American Evacuation and Resettlement: A Digital Archive, The Bancroft Library, University of California Berkeley, call number BANC MSS 67/14 c, folder W 1.80:07**, accessed on Oct. 15, 2014 at http://digitalassets.lib.berkeley.edu/jarda/ucb/text/cubanc6714_b303w01_0080_07.pdf .
- Burton, et al., 105–06.
- Existing studies that explore block politics include Arthur A. Hansen's "Cultural Politics in the Gila River Relocation Center, 1942-1943," Arizona and the West 27 (Winter 1985): 327-62; Brian Masaru Hayashi's Democratizing the Enemy: The Japanese American Internment (Princeton: Princeton University Press, 2004); and Nishimoto's Inside An American Concentration Camp .