Today's guidon traces its heritage back to smaller flags used by cavalry units in Europe during the late 1700s and early 1800s; these were used by squadrons within a larger regimental formation both on the battle field and in camps. The guidon came to the U.S. Army in 1834 with the first cavalry units originally called dragoons. The top half was red and the bottom half white with the letters U.S. in white on the red and the company letter in red on the white. This design remained essentially unchanged until 1862, which was early in the Civil War. The shape didn't change but the cavalry guidon colors were changed to a stars and stripes pattern. Insignia and lettering for Aviation Depot units changed to white in 1931 and by 1945, the color for insignia and letters and numbers on squadron guidons was changed to Air Force yellow. This design remained in use by the U.S. Air Force even after they became a separate service. It wasn't until Dec. 21, 1962, that the yellow eagle we see today was adopted for use on the guidon in place of the winged propeller.
