III Corps (Union Army)

III Corps
III Corps badge
Active	1862–1864
Type	Army Corps
Size	Corps
Part of	Army of the Potomac
Engagements	American Civil War Peninsula Campaign Yorktown Battle of Williamsburg Battle of Fair Oaks Seven Days Battles Battle of Oak Grove Battle of Glendale Battle of Malvern Hill Battle of Fredericksburg Battle of Chancellorsville Battle of Gettysburg Mine Run Campaign
Commanders
Notable commanders	Daniel E. Sickles
Insignia
1st Division
2nd Division
3rd Division

There were four formations in the Union Army designated as III Corps (or Third Army Corps) during the American Civil War.

Three were short-lived:

• In the Army of Virginia, a temporary designation of the command better known as I Corps (Army of the Potomac)::
  • Irvin McDowell (June 26 – September 5, 1862);
  • James B. Ricketts (September 5–6, 1862);
  • Joseph Hooker (September 6–12, 1862)
• In the Army of the Ohio:
  • Charles C. Gilbert (September 29 – October 24, 1862)
• In the Army of the Cumberland:
  • Charles C. Gilbert (October 24 – November 5, 1862)

The other, the III Corps, Army of the Potomac (March 13, 1862 – March 24, 1864), is the subject of this article.