The Army officially adopted this hat for campaigns in 1876 and it is what cavalry soldiers looked to for inspiration in headgear. It was available in drab and dark blue (drab more prevalent among enlisted men). It lasted about 10 years.
For those of you who believe John Ford knew anything about US Army uniforms during the Indian Wars, here is what the museum contends is an unauthorized officer's hat that was worn on the frontier. Description from curtrich.com. I searched for this on bing.com/images
ULTRA RARE 1876 PATTERN US ARMY CAMPAIGN HAT. Adopted in 1876, this black felt hat became symbolic of the Army on the western frontier and today is one of the most highly prized pcs of military headgear. It has a brim measuring approx 2-3/4″ wide with the edge turned and sewn with two rows of stitching. The crown measures approx 6″ high. There are metal vents in the left and right sides of the crown. This hat comes complete with an 1858 worsted Cav. hat cord and brass 1872 crossed sabers.
Union Infantry Officer's Kepi Dark blue wool blue body with black velvet band. Finish very worn. Black enameled bound leather on pasteboard visor lined in green grained leather; black enameled leather chin strap with brass wire buckle and eagle side buttons. Obverse has applied gold bullion embroidered infantry bugle insignia on wool with false bullion metal regimental numbers "17." Interior has gauze lining with leather crow