OVERLAND COMPANIES, or wagon trains, traveled from the Missouri River to California or Oregon. Beginning in 1839, most traveling groups were families. During the gold rush, single men joined joint-stock companies, paying $300 to $500 for passage. Groups organized prior to starting, sometimes with written constitutions and bylaws. Once underway, overlanders might join another group for various reasons. After 1850, eastbound companies were not uncommon. Initially, companies hired experienced mountain men as guides. After 1850 the routes were well worn, guidebooks were available, and experienced travelers were willing to guide others. Over a quarter of a million emigrants passed over the trails in two decades.
Unruh, John D., Jr. The Plains Across: The Overland Emigrants and the Trans-Mississippi West, 1840–60. Urbana: University of Illinois Press, 1993.