A new advance of the American fur-trader was made when Jedediah Smith succeeded Ashley as the leader in Rocky Mountain trade and exploration. In 1826 he left the Salt Lake rendezvous with a party of trappers to learn the secrets of the lands between the Rocky Mountains and the Pacific Ocean. Proceeding to the southwest along the Virgin River, Smith descended it to the Colorado, and crossed the desert to San Diego, California. Here, by the intercession of a Yankee captain then in that port, he obtained supplies from the Spaniards, and turned to the northwest, traveling parallel to the coast for some three hundred miles to wintering grounds on the headwaters of the San Joaquin and the Merced. Leaving most of his party behind, he crossed the mountains, by a route south of the Humboldt, and returned to Great Salt Lake.

Almost immediately he set out again for California by the previous route, and in 1827 reached the San Jose mission. Here he was arrested by the Spanish authorities and sent under guard to Monterey, where another Yankee skipper secured his release. Wintering once more in California, this time on the American Fork, he reached the coast in the spring of 1828, and followed the Umpquah River towards the Oregon country. While he was absent, his camp was attacked by the Indians and fifteen of his men killed. Absolutely alone, Smith worked his way through the forest to Fort Vancouver, where he enjoyed the hospitality of Dr. McLoughlin through the winter. In the following spring he ascended the Columbia to the Hudson Bay posts among the Flatheads, and made his way in the summer of 1829 to the rendezvous of his company at the Tetons. In three years this daring trader, braving the horrors of the desert and passing unscathed from Indian attacks which carried off most of his companions, opened to knowledge much of the vast country between Great Salt Lake and the Pacific. [Footnote: H. H. Bancroft, California, III., 152-160, citing the sources.] In 1831, while on the Santa Fe trail, Smith and his companions lost their way. Perishing with thirst, he finally reached the Cimaron, where, as he was digging for water in its sandy bed, he was shot by an Indian.

Thus the active men of the Rocky Mountain Fur Company, in the decade between 1820 and 1830, revealed the sources of the Platte, the Green, the Yellowstone, and the Snake rivers, and the characteristics of the Great Salt Lake region; they pioneered the way to South Pass, descended Green River by boat, carried cannon into the interior basin; showed the practicability of a wagon route through the Rockies, reached California from Salt Lake, crossed the Sierras and the deserts of Utah and Nevada, and became intimately acquainted with the activity of the British traders of the northwest coast. [Footnote: Chittenden, Am. Fur Trade, I., 306.]

Already an interest in Oregon and the Rocky Mountain region was arising on the eastern seaboard. In 1832, Captain Bonneville, an officer in the United States army, on leave of absence, passed with a wagon-train into the Rocky Mountains, where for nearly three years he trapped and traded and explored. [Footnote: Irving, Bonneville.] Walker, one of his men, in 1833, reached California by the Humboldt River (a route afterwards followed by the emigrants to California), and made known much new country. A New England enthusiast, Hall Kelley, had for some years been lecturing on the riches of the Oregon country and the need of planting an agricultural colony there. It was natural that Boston should be interested in the Oregon country, which was visited by so many vessels from that port. In 1820, New England missionaries settled in the Hawaiian Islands, closely connected by trade with the coast. In 1832, Nathaniel Wyeth, of Cambridge, Massachusetts, led a party of New-Englanders west, with the plan of establishing a trading and fishing post on the waters of the Columbia. [Footnote: Chittenden, Am. Fur Trade, I., 435; Wyeth's "Journals" are published by the Oregon Hist. Soc.; cf. Irving, Bonneville, chap. vi.]