A guidon is a military standard, or flag, that Regiments carry to signify their unit designation and corps affiliation or the title of the individual who carries it.
The significance of the guidon is that it represents the unit and its commanding officer. When the commander is in, his guidon is displayed for everyone to see. It is an honor to be the guidon carrier for a unit. He stands in front of the unit alongside of the commander and is the rallying point for troops to fall into formation when the order is given. In drill and ceremonies, the guidon and commander are always in front of the formation.
The guidon is a great source of pride for the unit, and several military traditions have developed around it, stemming back from ancient times.
This photograph shows a group of four Buffalo Soldiers on horseback with the United States Flag and the Regiment’s guidon.
2013.35.3, Courtesy of The National Archives