When we published “U.S. Army Infantry Divisions, 1943-45”, in 2010, we stated that the book was the first part of a two-volume series on the U.S. Armored Divisions in WWII. The U.S. Army committed in battle 16 armored divisions, but two of them stayed organized under the obsolete organization of 1942. The study of the organization of 1942 stayed to do, to have a complete overview of the U.S. Armored Divisions in WWII. This is done with this book in which the author presents an extremely detailed record of the organization, doctrine, and equipment of the Armored Division, from the reorganization on 1 January 1942, under the Armored Force Revision dated 22 December 1941, to the official organization under the Tables of Organization dated 1 March 1942, and the changes occurring in 1943. Because of the size of this work, it is presented in two volumes. In Volume 1, the author examines each unit and sub-unit of the division, from Division Headquarters to the Band. A chapter is dedicated to each principal unit: Armored Reconnaissance Battalion, Armored Regiment, Armored Infantry Regiment, Armored Field Artillery Battalion, Armored Engineer Battalion, and Armored Signal Company. Rear-area units, generally overlooked or forgotten are also included. For each unit, the author examines their organization, down to the lowest level, and their tactical doctrine as described in contemporary field manuals. Each sub-unit, including section and squad, is presented by lists of personnel with rank and duty, individual weapons, vehicles with armament and radio sets, and organizational equipment, individual and common. At battalion and company levels, the author studies the doctrine of employment of the unit, in offensive, defensive, and security missions, as well as the duties of key personnel. The book includes 171 charts depicting the general organization of each unit but also a detailed organization showing all vehicles with crew members, on the march, in combat, and at work when those positions are known. Charts also depict the radio nets from division level down to company level. The Volume 2 will continue the study of the organization of 1942 with the remaining units: Division Trains Headquarters, Maintenance battalion, Armored Medical Battalion, and Supply Battalion. The second part of the Volume 2, will show, principally with charts, the organization of the Heavy Armored Division in 1944-1945, especially that of the 2nd and 3rd Armo