The Trail of Jedediah Smith From 1826-27:
From the time that Jedediah Smith left the rendezvous in July, 1826 until arriving at the following years rendezvous on July 3, 1827, he and his party were inside the territory claimed by Mexico. Although the area which would become Utah, Nevada, and much of eastern California was unoccupied, and unsettled, this harsh, desert region was important to the authorities of Mexico as a buffer zone to keep potential enemies, the French, and later the English and Americans at bay.
When Jedediah Smith and his party staggered out of the Mojave Desert into San Bernadino Valley, the authorities of Mexico were extremely suspicious of his motives. It was not possible to accidentally cross a thousand or so miles of desert, in search of beaver that weren’t there. To the authorities thinking, although not certain, there was a high probability that he was a spy. Jedediah was probably in part saved from incarceration by his partnership with William Ashley (a General, albeit in the Missouri Militia) and his trading (trapping) license signed by William Clark (of Lewis and Clark, now an official with the Federal Government)
Finally Jedediah was released, under the promise that he leave California the way he entered. In part determined to avoid the nearly deadly crossing of the Mojave Desert and harsh regions which would become Utah, Jedediah proceeded to leave through the settled regions as promised, but then headed north along the east flank of the Sierra Nevada Mountains. He was also searching for the Rio Beunaventura, a river believed to run from the continental interior to the Pacific.
With time running out to return to the rendezvous of 1827, he was faced with a decision. Unable to locate the river, or even a suitable place to cross the Sierra Nevada Mountains, he left most of his men behind, and taking two others forced a passage across the mountains. The trail across Nevada and Utah was nearly as bad as that taken to California, and Jedediah and his two companions nearly died of thirst before reaching the vicinity of Salt Lake.