On March 20, 1822, the Missouri Republican published a notice addressed "to enterprising young men" in the St. Louis area. "The subscriber," it said "wishes to engage one hundred young men to ascend the Missouri River to its source, there to be employed for one, two, or three years. For particulars enquire of Major Andrew Henry... or of the subscriber near St. Louise." The "subscriber" was General William H. Ashley, and among the "enterprising...