There have been a number of 18th Divisions in the history of the United States Army:
18th Division – A National Guard division established in early 1917 consisting of Arkansas, Louisiana, and Mississippi. By the end of that same year, the 18th Division became the 39th Division (later 39th Infantry Division).
18th Division (World War I) – Organized in 1918 as a regular army and national army division for World War I, the 18th Division did not go overseas and demobilized in February 1919 at Camp Travis, Texas. Both of these two divisions would likely have included the 35th Infantry Brigade and the 36th Infantry Brigade.
18th Armored Division – Placed on rolls for World War II, the 18th Armored Division was never organized.
18th Airborne Division – a "phantom" division in World War II.
