The official history of the US Army in World War One is available as PDF as well as HTML. We´ve linked to the HTML versions, but you can easily access the PDF versions from the Center of Military History´s Website.

Order of Battle of the United States Land Forces in the World War

Volume 1: General Headquarters, Armies, Army Corps, Services of Supply, and Separate Forces,

Volume 2; Divisions

Volume 3, part 1: Organization and Activities of the War Department

Volume 3, part 2: Territorial Departments, Tactical Divisions Organized in 1918, and Posts, Camps, and Stations

Volume 3, part 3: Directory of Troops

United States Army in the World War, 1917-1919

Volume 1: Organization of the American Expeditionary Forces
Narrative account of the AEF’s participation in major operations

Volume 2: Policy-forming Documents of the American Expeditionary Forces

Volume 3: Training and Use of American Units With the British and French

Volume 4: Early Military Operations of the American Expeditionary Forces
Cambrai Nov 20 – Dec 4 1917, Somme Defensive Mar 21 – Apr 6 1918, Lys Apr 9 – Apr 27 1918, Aisne Defensive May 27 – Jun 5 1918, Cantigny Apr 12 – Jun 2 1918, Château-Thierry Jun 6 – Jul 5 1918 (Belleau Wood Jun 6 – 25 1918, Vaux Jun 26 – Jul 3 1918), Montdidier-Noyon June 9-13 1918

Volume 5: Military Operations of the American Expeditionary Forces
Champagne-Marne July 15 – 18 1918, Aisne-Marne July 18 – Aug 6 1918

Volume 6: Military Operations of the American Expeditionary Forces
Oise-Aisne Aug 7 – Nov 11 1918, Ypres-Lys Aug 19 – Nov 11 1918, Vittorio-Veneto Oct 24 – Nov 4 1918

Volume 7: Military Operations of the American Expeditionary Forces
Somme Offensive Aug 8 – Nov 11 1918

Volume 8: Military Operations of the American Expeditionary Forces
St-Mihiel Sept 12 – 16 1918, Meuse-Argonne Sept 26 – Nov 11 1918

Volume 9: Military Operations of the American Expeditionary Forces
Meuse-Argonne Sept 26 – Nov 11 1918

Volume 10-1: The Armistice Agreement and Related Documents

Volume 10-2: The Armistice Agreement and Related Documents

Volume 11:  American Occupation of Germany
Nov 1918 – July 1919;  German Campaign Plans Oct 29 – Nov 11 1918

Volume 12: Reports of the Commander-in-Chief, AEF, Staff Sections and Services

Volume 13: Reports of the Commander-in-Chief, AEF, Staff Sections and Services

Volume 14: Reports of the Commander-in-Chief, AEF, Staff Sections and Services

Volume 15: Reports of the Commander-in-Chief, AEF, Staff Sections and Services

Volume 16: General Orders, GHQ, AEF

Volume 17: Bulletins, GHQ, AEF