1870’s cover to St Croix County, Wisconsin, with a 3c tied by a concentric circle cancellation with a very fine strike of the scarce FORT RANDALL AUG 10 DAK. cancel. There are no other transit or arrival markings. Its strategic location along the Missouri River made it a key fort in two lines of western frontier defense. It was the last link in a chain of forts protecting the overland route along the Platte River. It was also the first fort in a chain of forts on the upper Missouri River. An appealing cover.