What was Americas first sniper rifle and what war was it first used in?

According to Gun Digest, it was the American Long or "Kentucky" rifle, used in the American War of Independence. Not often, as with all muzzle loaded weapons it was slow, the grooves could foul after relatively few shots requiring the entire weapon to be stripped down and cleaned to regain a measure of accuracy, and you couldn't couple it with a bayonet so in the event of an infantry charge you were screwed.