Companies of American fur trappers were the trail blazers for subsequent explorers, gold rushers and settlers. Caught in the spell of a wild, free life, they were wide-ranging rovers. Trapping parties setting out from Taos, New Mexico, might hunt on the Yellowstone and Snake Rivers or cross to California and trap on the San Joaquin or Sacramento Rivers. Their lives beyond the outer fringes of civilization were hard, lonely, and beset with danger from grizzly bears, Indian attacks, floods and snow slides; or brawls among themselves. The passes they crossed, the routes they discovered, and the valleys where they held their rendezvous became the routes and stopping places others followed, even the railroads. Some developed the historic trade between St. Louis, Santa Fe, and Chihuahua; a few opened trade in horses and mules between California, New Mexico, Louisiana, and Missouri. By the mid-1840s, when the fur trade declined, these adventurous mountain men became emigrant guides to caravans of covered wagons, Army scouts, or professional hunters.