This is a list of the top 10 places in Iowa, by size, served by one high school, in five-year increments. In most cases, it involves whole-grade sharing followed some time later by consolidation, but in some cases there is only one-way sharing, where a district sends grades 7-12 or 9-12 to the larger school. Those cases are indicated by “plus” in the text.
NOTE 6/27/16: Western Dubuque, 554 square miles, has two high schools, Western Dubuque and Cascade. It has been the largest school district in Iowa since 1960. Areas are based on a list from the Iowa Department of Management, rounded to the nearest square mile (or tenth if necessary).
Fall 2001: Davis County, 463; Howard-Winneshiek, 426; Allamakee, 423; Mount Ayr, 383; Maple Valley-Anthon-Oto, 374; Fairfield, 359, Albia, 338; Benton Community, 332; South O’Brien, 305; North Iowa, 296.
2006: Davis County, 463; Howard-Winneshiek, 425; Allamakee, 423; Mount Ayr, 383; Maple Valley-Anthon-Oto, 374; Clarion-Goldfield plus Dows, 362; Fairfield, 359; Van Buren, 352; Albia, 338; Benton Community, 332.
2011: Davis County, 463; Howard-Winneshiek, 425; Allamakee, 423; Pocahontas Area/Pomeroy-Palmer, 402; Mount Ayr, 383; Maple Valley-Anthon-Oto, 374; Chariton, 374; Sioux Central plus Albert City-Truesdale (adding part of South Clay), 373; Clarion-Goldfield plus Dows, 362; Fairfield, 359.
2016: Algona plus LuVerne, 550; North Union (Armstrong-Ringsted merged with Sentral, sharing with North Kossuth), 540; Van Buren plus Harmony, 520; Southeast Valley (Prairie Valley plus Southeast Webster-Grand), 498; Davis County, 463; Mount Ayr, 425.4; Howard-Winneshiek, 424.6; South Central Calhoun, 424.3; Allamakee, 423; Webster City plus Stratford plus Northeast Hamilton, 422.
2021: MVAOCOU (Maple Valley-Anthon-Oto plus Charter Oak-Ute), 553; Algona plus LuVerne, 550; Pocahontas Area plus Laurens-Marathon, 549; North Union plus North Kossuth, 540; Van Buren County, 532; Southeast Valley, 498; Davis County, 463; Mount Ayr, 425.4; Howard-Winneshiek, 424.6; South Central Calhoun, 424.3. (Four more are in the 410-424 range.)
UPDATE 3/5/22: Now with fall 2021 numbers. Sometime between 2016 and 2019, Davis County and Van Buren swapped 11½ square miles, but I don’t know more. Also, Howard-Winneshiek and Mount Ayr got tweaked juuuust enough to switch places.
UPDATE 7/7/22: After some correspondence, I have updated the size of Davis County throughout. The Department of Education’s 2016 map and Department of Management’s 2016 database appear to have been in error.