The matter of divisional assignment was generally up to the needs of the military, although the circumstances of individual soldiers at specific points in time could have some bearing upon which division they ended up assigned to if that was where they were destined to serve.

In 1920, the Army divided the United States into nine “corps areas” for command and control purposes, overseen by four field armies. Each corps area, roughly equal in population, supported one Regular Army division, two National Guard divisions, and three Organized Reserve divisions, organized into two army corps.

Corps area	States	Army corps and divisions
1	Connecticut, New Hampshire, Maine, Massachusetts, Rhode Island, Vermont	I Corps: 9th, 26th, 43rd; XI Corps: 76th, 94th, 97th
2	Delaware, New Jersey, New York	II Corps: 1st, 27th, 44th; XII Corps: 77th, 78th, 98th
3	Maryland, Pennsylvania, Virginia, Washington, D.C.	III Corps: 8th, 28th, 29th; XIII Corps: 79th, 80th, 99th
4	Alabama, Arkansas, Florida, Georgia, Tennessee, Mississippi, North Carolina, South Carolina	IV Corps: 4th, 30th, 31st; XIV Corps: 81st, 82nd, 87th
5	Indiana, Kentucky, Ohio, West Virginia	V Corps: 5th, 37th, 38th; XV Corps: 83rd, 84th, 100th
6	Illinois, Wisconsin, Michigan	VI Corps: 6th, 32nd, 33rd; XVI Corps: 85th, 86th, 101st
7	Iowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota, South Dakota, Wyoming	VII Corps: 7th, 34th, 35th; XVII Corps: 88th, 89th, 102nd
8	Arizona (partially), Colorado, New Mexico, Oklahoma, Texas	VIII Corps: 2nd, 36th, 45th; XVIII Corps: 90th, 95th, 103rd; 1st Cavalry Division
9	Arizona (partially), Idaho, Montana, Nevada, Oregon, Utah, Washington, Wyoming	IX Corps: 3rd, 40th, 41st; XIX Corps: 91st, 96th, 104th

Arkansas was transferred from the Fourth to the Seventh Corps Area on 1 December 1920. Arizona was under the control of the Eighth Corps Area, but its southwestern part was attached to the Ninth Corps Area. Minor reshuffling occurred when the Army Service Forces were created in March 1942 and the corps areas were renamed service commands in July; Arkansas moved to the control of the Fourth Service Command, Colorado moved to the Seventh Service Command, and the Ninth Service Command controlled the whole of Arizona.

The Regular Army:

During the interwar period (1919-1941), the infantry divisions of the Regular Army (1st-9th stateside, Hawaiian, Panama Canal, and Philippine located at their geographic namesakes) although they nominally drew their personnel from all over the United States, had formed something approximating regional “identities” due to their posts. The 1st, 2nd, and 3rd Divisions were the only truly active stateside Regular Army divisions during this period; the headquarters of the 1st and 3rd Divisions basically ceased to exist, but were repopulated by the late 1920s. The divisions’ subordinate units, operating on their own, were widely scattered throughout their allotted geographic areas, and sometimes were assigned to Army posts in completely different corps areas to receive training, especially as preparations for potential war were made in the late 1930s. An exception was the 2nd Division, fully active and concentrated to watch the Mexican border for the majority of the interwar period at Fort Sam Houston, Texas.

The 4th through 9th Divisions were partially inactivated after Congress realized it would be impossible to maintain nine full divisions, and were represented in the active Regular Army by their even-numbered infantry brigade and select supporting units. A 1927 plan to assign the active brigades of these divisions to the 4th through 6th Divisions only fell through by 1933, and they remained basically reinforced brigades. Corps area commanders took it upon themselves to maintain readiness and organize their dormant divisions (these divisions were not assigned a general officer while inactive, the corps area commander acting as such) as they saw fit, and the inactive units of these divisions were authorized to be organized with personnel of the Organized Reserve.

Division	Headquarters location	States in which subordinate units stationed, 1923 and 1939 (predominant bolded)
1st	Camp Zachary Taylor, KY, 1919-20; Camp Dix, NJ, 1920-22; Fort Hamilton, NY, 1922-39; Fort Benning, GA, 1939-40; Fort Hamilton, NY, 1940-41; Fort Devens, MA, 1941	Maryland, New York, Pennsylvania, Vermont
2nd	Fort Sam Houston, TX, 1919–41	Colorado, North Carolina, Texas, Wyoming
3rd	Camp Pike, AR, 1919-21; Fort Lewis, WA, 1921-41	California, Utah, Washington, Wyoming
4th	Camp Dodge, IA, 1919-20; Camp Lewis, WA, 1920-21; Inactive, 1921-27; Fort McPherson, GA, 1927-40; Fort Benning, GA, 1940-41	Alabama, Georgia, North Carolina, Oklahoma, South Carolina, Texas, Virginia
5th	Camp Gordon, GA, 1919-20; Camp Jackson, SC, 1920-21; Inactive, 1921–26; Fort Benjamin Harrison, IN, 1926-27; Columbus, OH, 1927-39; Fort McClellan, AL, 1939-40; Fort Custer, MI, 1940-41	Georgia, Indiana, Kentucky, Ohio
6th	Camp Grant, IL, 1919-21; Inactive, 1921-26; Chicago, IL, 1926-39; Fort Lewis, WA, 1939-40; Fort Jackson, SC, 1940; Fort Snelling, MN, 1940-41; Fort Leonard Wood, MO, 1941	Illinois, Missouri, Wisconsin
7th	Camp Funston, KS, 1919-20; Camp George G. Meade, MD, 1920-21; Inactive, 1921-40; Fort Ord, CA, 1940-41	Iowa, Kansas, Minnesota, Nebraska, Virginia
8th	Camp Lee, VA, 1919; Inactive, 1923–26; Philadelphia, PA, 1926-40; Fort Jackson, SC, 1940-41	Georgia, Maryland, New Jersey, New York, Pennsylvania, Virginia
9th	Inactive, 1923-26; Army Base, Boston, MA, 1926-40; Fort Bragg, NC, 1940-41	Maine, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island