American Civil War Corps Badges

Corps badges in the American Civil War were originally worn by soldiers of the Union Army on the top of their army forage cap, left side of the hat, or over their left chest pocket. The idea was suggested by Major Geneneral Philip Kearny. During a battle he reprimanded officers that turned out to not be under his command. To prevent that from happening again, he ordered the men in his division to sew a square of red cloth on their hats. This idea was adopted by Major General Joseph Hooker after he assumed command of the Army of the Potomac. This was so any soldier could be identified at a distance.
Corps badges.
Maj. Gen. Daniel Butterfield, Hooker's chief of staff, was assigned the task of designing a distinctive shape for each corps badge. Butterfield also decided that each division in the corps should have a variation of the corps badge in a different color. Division badges were colored as follows:
These were used in the United States' Army of the Potomac. These rules were adopted by other Union Armies, however it was not universal. For example, the XIII Corps never adopted a badge. Also, the XIX Corps had the first division wear a red badge, the second division wear a blue badge, and the third division wear white.
For Army corps that had more than three divisions, the standardization was lost:
The badges for enlisted men were cut from colored cloth. Officer's badges were privately made and of a higher quality. Metallic badges were often made by jewelers and were personalized for the user. The badges eventually became part of the Army regulations and a great source of regimental pride.
XIX XX XXI XXII XXIII XXIV XXV Cavalry corps
Corps flags, other Union armies.
XIII Corps, Army of the Tennessee.
No badge was designated for the XIII Corps.
Brigade badges.
I Corps, Army of the Potomac