The divisions the American Expeditionary Force used during World War I were very large, over 28,000 men. In contrast, the standard infantry division configuration for the French and German Armies had around 14,000 men, the British, around 18,000.

General John J. Pershing fixed the size of his new divisions at 979 officers and 27,082 enlisted men. Permanent infantry divisions were a new concept in the United States military; previously, "divisions" were only used as an organizational tool between the regiment and the corps, particularly during the American Civil War.

The 8th Division (8th Infantry Division) was organized as follows during World War I. Only some units of the division landed in France before the Armistice, and none saw combat. The US divisional organizations, as a basis followed a "square" pattern, but changed many times in the small details during their time of involvement in World War I, as can be seen in my first link; this is only a snapshot in time.

Organization:

• Divisional Headquarters

• 15th Infantry Brigade

• 12th Infantry Regiment

• 62nd Infantry Regiment

• 16th Infantry Brigade

• 8th Infantry Regiment

• 13th Infantry Regiment

• 22nd, 23rd and 24th Machine Gun Battalions

• 8th Field Artillery Brigade

• 8th Trench Mortar Battery

• 2nd Artillery Regiment

• 81st Artillery Regiment

• 83rd Artillery Regiment

• 319th Engineer Regiment and Train

• 320th Field Signal Battalion and Train

• Military Police Company

• 8th Division Train Headquarters

• 8th Ammunition Train

• 8th Supply Train

• 8th Sanitary Train

• 11th Ambulance and Field Hospital Company

• 31st Ambulance and Field Hospital Company

• 32nd Ambulance and Field Hospital Company

• 43rd Ambulance and Field Hospital Company

Sources:

United States Army in the World War 1917-19; Organization of the American Expeditionary Forces Volume I PDF

American World War I order of battle

Square division organization