 Soon after Lewis and Clark returned to St. Louis in 1806, they brought word of large numbers of beaver in present-day Montana. That perked the ears of many trappers. Beaver were used for high-fashion hats, top hats, tall hats, like think of an Abraham Lincoln type hat. Beaver was very valuable at the time. Word spread quickly, oh, there's a new source of beaver. And so men started going up from St. Louis up the Missouri River. But relations with the Native Americans in that area were not conducive to trapping there.