The U.S. Army has 23 corps, four of which are active. I Corps is a member of USARPAC, or U.S. Army Pacific Command. I Corps has a distinguished history, dating back to the American Civil War.
In the Civil War, this corps was probably the most distinguished and veteran corps in the entire Union Army. It was commanded by very distinguished officers. It was created in March 1862, when President Abraham Lincoln ordered the creation of a four-corps army, then under the command of Major General George B. McClellan. The first commander of this corps was Major General Irvin McDowell, containing three divisions. It was held in defense of Washington, while the rest of the Army of the Potomac advanced to the Peninsular Campaign.
It was then consolidated in the Army of Virginia under Major General John Pope, and fought in the Battle of 2nd Manassas, as the Third Corps, Army of Virginia. Afterwards, its name was restored. Then, it rejoined the Army of the Potomac, and crossed the Potomac River into Maryland to fight in the Battle of Antietam, under Major General Joseph Hooker. There, the division of Pennsylvania Reserves, under Brigadier General George G. Meade took heavy casualties through its hard fighting, and was withdrawn to replenish.
The command of the army then changed to Major General Ambrose E. Burnside, and they moved southward to fight General Lee's army at the Battle of Fredericksburg, where it was commanded by Major General John F. Reynolds, arguably the best eastern Union corps commander. He superbly led the corps through this battle, then through the Battle of Chancellorsville, with the army being led by General Hooker, who left this superb corps in reserve.
At the Battle of Gettysburg, the last major battle of this corps, General Reynolds was killed near the beginning of the battle, and command was inherited by Brigadier General Abner Doubleday. The next day (July 2, 1863), the command was given to Major General John Newton, who led it through this battle, and through the Mine Run battles. Afterwards, the corps was disbanded and absorbed into the rest of the army, in a reorganization, partly under the leadership of Lieutenant General Ulysses S. Grant. Here, the career of this corps was ended.
The corps was reactivated in 1898, under the leadership of Major General John R. Brooke, and elements landed on July 31, 1898 to take part in the Puerto Rico Campaign. It advanced to Guayam, where it fought a battle on August 5, but the armistice was signed before they could partake in a slated major attack.
Following the American declaration of war on the country of Germany, on April 6, 1917, the I Corps was the first unit activated, and moved into the war in Europe. Its subordinate units were shipped to Europe, and the Corps was deactivated. However, it was reactivated again on January 15, 1918, in Neufchateau, France. Assisted by the French XXXII Corps, the headquarters was organized and trained; on January 20, Major General Hunter Liggett took command.
In February, the corps consisted of the 1st, 2nd, 26th, 32nd, 41st, and 42nd Divisions. From February to July, 1918, the German Army launched four major offensives, attempting to secure victory before the full American force could be brought to bear. The final offensive, started in July 1918, was an attempt to cross the Marne, in the area of Chateau-Thierry, but the American lines (including I Corps) held, and the offensive was fought back. Thereafter, the I Corps, along with other U.S. and Allied units, moved forward, breaking the German will to fight, until the armistice, signed on November 11, 1918.
The I Corps continued to train in France, until it was deactivated on March 25, 1919.
Sub-Units
1st, 2nd, 3rd, 4th, 5th, 6th, 26th, 28th, 32nd, 35th, 36th, 41st, 43rd, 77th, 78th, 80th, 82nd, 90th, 91st, and 92nd American Divisions.
62nd, 167th, and 5th Cavalry French Divisions.
The current order of battle of I Corps is somewhat muddy.
Official Information from I Corps site
History
The Civil War
The Spanish-American War
World War I
World War II
Japanese Occupation
Korean War
Current Order of Battle
Likely Subordinate Units
*These units are technically under divisional command, and are arbitrarily assigned to brigades
Likely Subordinate National Guard/Reserve Units
