The 82nd Airborne Division was originally the 82nd Infantry Division of the Organized Reserve, and after being ordered into active military service on 25 March 1942, was converted to an airborne division on 15 August 1942. The 101st Infantry Division was disbanded in the Organized Reserve on 15 August 1942, and was concurrently reconstituted and activated as an airborne division on the same date.

The 15th Airborne Division was constituted, but never activated. It was dropped from the mobilization program in 1943.
The 19th Armored Division was constituted, but never activated. It was dropped from the mobilization program in 1943.
Infantry divisions were initially titled with their numerical designation and "division" (e.g., "1st Division"). In August 1941, the War Department issued a statement that divisions' names were to represent their major arm of service (i.e., armored, cavalry, or infantry) to avoid confusion as several divisions of different arms now shared the same number. Some divisions issued general orders introducing "infantry" as an official part of their names, but this change was not added to the table of organization of the infantry division, which technically controlled its naming conventions, until 1 August 1942.

The 1st through 25th Infantry Divisions, excepting the 10th Mountain Division, were raised in the Regular Army or the Army of the United States prior to American involvement in World War II. Because of funding cuts, in September 1921, the 4th through 9th Infantry Divisions were mostly inactivated. Within a few years, the headquarters of the 1st and 3rd Infantry Divisions "almost ceased to exist. Only the division commander and a few staff officers remained to carry out minimal division administrative functions, and neither division exercised true command functions over their units." The 2nd Infantry Division remained the most functional stateside division, as it was concentrated entirely at Fort Sam Houston, Texas. By the mid-1920s, most of the divisions' inactive units were staffed with Organized Reserve officers as "Regular Army Inactive" units.

The Hawaiian Division, "which was the closest thing to a full-strength division in the interwar American Army." was split on 1 October 1941 to create the 24th and 25th Infantry Divisions. The 24th Infantry Division headquarters inherited the lineage of the Hawaiian Division's headquarters, while the 25th Infantry Division was raised in the Army of the United States.

The 10th Mountain Division was raised in the Army of the United States in 1943.
The 26th through 45th Divisions, with the exception of the 39th and 42nd Divisions, were raised in the National Guard during and after World War I. In postwar mobilization plans, the 26th through 45th Divisions, less two, were allotted to the National Guard. The 30th, 31st, and 39th Divisions had been organized in what would become the states of the Fourth Corps Area; the designations of the 30th and 39th Divisions were originally selected, with the 31st Division being deleted. In 1923, the adjutants general of the states concerned successfully requested that the War Department change the designation of the 39th Division to the 31st Division and adjust allotments of units accordingly. The 42nd Division was the second division deleted from the mobilization program as it had contained units from twenty-six states and the …

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