Before 1841 most settlers traveled to California and the Pacific coast by sea. Books and newspaper reports from explorers and visitors to the far west roused the public's interest in an overland route. One trapper, Antoine Robidoux, who returned from California, described it as "a perfect paradise, a perpetual spring." One of the first organized overland wagon trains left the Missouri frontier in May 1841 with seventy people and a dozen wagons bound for the Pacific. By 1846 thousands of pioneers were taking the overland route west. By the 1850s the trails west were becoming so well traveled that in some places they were more than a mile wide.

Despite the glowing reports of the earthly Edens to be found in California and Oregon, the pioneers soon found the route to paradise was a hard six-month journey. Many rivers had to be crossed. The oxen, mules, and cattle...