A correction to my original post in this thread. I said "18th century" when noting when these horns were used. That, of course, should be the 19th century. Sorry.
You never know Stan, Horns and flasks became popular for carrying BP and other dried staples such as salt and sugar as early as the 15th. century, and they became an indispensable item in the American colonies from the 17th ~ 19th century, some of the larger horns were turned into drinking mugs and some fashioned to carry rum and other spirits.
Most of the early horns that survived are riddled with worm holes from years of neglect, but some that still retained powder (bugs don't like gun powder) have survived pretty well intact, I have one that was shipped to the colonies from England before the Rev. War, probably to service British troops during the F&I war, the grain of the horn is very thick because cattle back then weren't as well kept as cattle are today, and the horn is dyed with a greenish tint from the brine that they shipped in in barrels aboard British ships, the brine was to keep the horns from smelling bad and to keep the bugs and ships pests from eating them away.
My horn was found along with a Third model Brown Bess used in the war of 1812, it's believed that the owner either picked it up in battle or was one of the British soldiers that deserted and stayed in the country after the British army were driven out, mine was found in a boarded up attic in Boston leaning against a chimney and the horn was found next to it still filled with powder, a shot pouch was also found but was pretty well eaten away, the Bess was still loaded with about a hundred grains of very crude powder and an equal amount of dried kernel corn (probably used for pest control in the garden), the horn was hanging from a Bayonet on a lanyard.
I bought the gun, horn, and bayonet from a friend who purchased it from the remodeling contractor that found it, I sold the Bess and it's bayonet to a friend who hounded me for several years and finally made me an offer I couldn't refuse, but I kept the horn and still have it, and it doesn't look like it's going on 260 years old.