Lt. Col. George Custer and the men of his 7th Cavalry Regiment went into the Battle of the Little Bighorn with flags flying, but they were wiped out, and nearly all their military artifacts were carried away by the victorious Lakota Sioux warriors.

Since 1895, the silk American flag, called a guidon, has been the property of the Detroit Institute of Arts, which has decided to sell it and use the proceeds to build its collection.

The guidon, discovered by Sgt. Ferdinand Culbertson while on a burial detail of the battlefield, has been valued at $2 million to $5 million and will be auctioned in October, Sotheby's auction house announced on Friday, the 134th anniversary of the battle.