Here's a photo of a expedition of group of 22nd Infantry to explore the Grand Canyon in 1879-1890. I got real interested in this expedition because the soldiers were mounted on mules (except officers) and I wanted "real bad" to not only do a proper impression but try and organize a "re-ride" from Ft.Lewis to the Grand Canyon.....provided we could get the Navajo's to cooperate....and possibly participate. My dream was to acquire a early trap door...original or repro. and enlisted man's uniform and equipment. After I had to put down my big cav mount "Dodger" up above Bayfield Colorado in the "Sunlight Basin" during a high country ML mule deer hunt, I started looking for ways to legitimately start using my mules in living history.
Notice some have boots on others are wearing canvas leggings......or it could be as simple as officer's wearing cav type boots and enlisted men infantry canvas leggings.
Here's some history.............we often forget the important role the infantry often played in the western expansion.http://1-22infantry.org/history3/7990.htm