Throughout the 1830s and in the early 1840s, travel increased through this pass. What Spanish-speaking settlers had long called “Mosca,” but traders and trappers began to call it “Robidoux Pass” as they were using it to access Fort Uncompahgre and others places farther west.

Lying between the Mountain Branch of the Santa Fe Trail and western Colorado, this trail came up Huerfano Creek, over Robidoux Pass, around the west end of Great Sand Dunes, up Saguache Creek, over Old Cochetopa Pass, and into the Gunnison River and Uncompahgre region. Pack trains over Robidoux Pass increased during the 1830s after Antoine Robidoux established another post in Utah. In 1837 the first wagon came over Robidoux Pass with a load of goods heading west.

This route was joined in the San Luis Valley by the trappers and pack trains who traveled north from Taos. A significant influx of pack trains on the circuitous North Branch also came from the mill on Arroyo Hondo where Simeon Turley began to produce Lightning in the early 1830s. 

Kit Carson was among the trappers who traveled northwest out of Taos. In the mid-1830s he located a camp on the Green River a little south of today’s Vernal, and the next year Antoine is said to have taken up what had been Kit’s camp.

Very soon Robidoux moved to a different location where a desultory trade had been conducted by a fellow named Reed, a few miles west of Vernal at today’s White Rocks. This became Robidoux’s Fort Uinta, commonly called Fort Winty.

(Robidoux’s name also appeared on a well-known pass on the Oregon Trail and on a nearby trading post near Scottsbluff, Nebraska. Replicas of that post and Fort Uncompahgre at Delta have been reconstructed and are tourist attractions.)

Marcus Whitman was forced by travel delays to stay at Fort Winty once and wrote a vivid description of its dissolute life and its denizens, who were indulging in every form of immorality. Soon afterward, irate Ute Indians burned both Forts Uncompahgre and Winty during a widespread uprising that took place in 1844.

By the mid-1840s Antoine Robidoux had accumulated heavy debts, especially to Simeon Turley and to the Bents of Bent’s Fort and Taos. He found escape from these troubles, though, when the U.S Army of the West marched into New Mexico in 1846, and Robidoux then hired on as an interpreter accompanying General Stephen Kearny to California, where Antoine suffered a debilitating wound.                                                                            

For a few years, his name continued to be attached to the route in the Sangre de Cristos. It was part of the trail from the Williams Fork of Huerfano Creek to the snowbound San Luis Valley when Fremont’s disastrous expedition went through in November 1848.

But this mountain passage soon became known as “Mosca Pass” again, and it seems unlikely that native New Mexicans had ever stopped using that name. And Mosca it would be called in 1871 when the territorial legislature granted a charter for a toll road to one Frank Hastings.

At the west end of the toll road, a post office called Orean and Montville operated between 1881 and 1900, and some pioneers’ covered wagons used the deteriorating route into the San Luis Valley, but the toll road’s charter reverted to the state about 1900. A notion to lay rails there died for lack of backers, and others wanted a road for motorized vehicles that never was built, although the pass was still accessible to jeeps when I first visited it.

Hikers on this pleasant trail in Great Sand Dunes National Park and Preserve can enjoy reflecting on the pass’ human and natural history, but watch out for hunters. It’s that season now.