Black Canyon of the Gunnison National Park

The Precambrian gneiss and schist that make up the majority of the steep walls of the Black Canyon formed 1.7 billion years ago during a metamorphic period brought on by the collision of ancient volcanic island arcs with the southern end of what is present-day Wyoming. The lighter-colored pegmatite dikes that can be seen crosscutting the basement rocks formed later during this same period.[7]

The entire area underwent uplift during the Laramide orogeny between 70 and 40 million years ago which was also part of the Gunnison Uplift. This raised the Precambrian gneiss and schist that makes up the canyon walls. During the Tertiary from 26 to 35 million years ago large episodes of volcanism occurred in the area immediately surrounding the present day Black Canyon. The West Elk Mountains, La Sal Mountains, Henry Mountains, and Abajo Mountains all contributed to burying the area in several thousand feet of volcanic ash and debris.[8]

The modern Gunnison River set its course 15 million years ago as the run-off from the nearby La Sal and West Elk Mountains and the Sawatch Range began carving through the relatively soft volcanic deposits.[8]

With the Gunnison River's course set, a broad uplift in the area 2 to 3 million years ago caused the river to cut through the softer volcanic deposits. Eventually the river reached the Precambrian rocks of the Gunnison Uplift. Since the river was unable to change its course, it began scouring through the extremely hard metamorphic rocks of the Gunnison Uplift. The river's flow was much larger than currently, with much higher levels of turbidity. As a result, the river dug down through the Precambrian gneiss and schist at the rate of 1 inch (25 mm) every 100 years. The extreme hardness of the metamorphic rock along with the relative quickness with which the river carved through them created the steep walls that can be seen today.[8]

A number of feeder canyons running into the Black Canyon slope in the wrong direction for water to flow into the canyon. It is believed that less-entrenched streams in the region shifted to a more north-flowing drainage pattern in response to a change in the tilt of the surrounding terrain. The west-flowing Gunnison, however, was essentially trapped in the hard Precambrian rock of the Black Canyon and could not change its course.[9]

In 1881, William Jackson Palmer's Denver and Rio Grande Railroad had reached Gunnison from Denver. The line was built to provide a link to the burgeoning gold and silver mines of the San Juan mountains. The rugged terrain precluded using 4 ft 8+1⁄2 in (1.435 m) standard rail; Palmer decided to go with the narrower 3 ft (0.91 m) gauge. It took over a year for Irish and Italian laborers to carve out a 15-mile (24 km) roadbed from Sapinero to Cimarron, costing a staggering $165,000 per mile. The last mile is said to have cost more than the entire Royal Gorge project.[11]

On August 13, 1882, the first passenger train passed through the Black Canyon. The editor of the Gunnison Review-Press rode in one of the observation cars; he remarked that the canyon was "undoubtedly the largest and most rugged canyon in the world traversed by the iron horse. We had often heard of the scenery of this canyon, but no one can have the faintest conception of its grandeur and magnificence until they have made a trip through it. It is a narrow gorge with walls of granite rising in some places to a height of thousands of feet ... Throughout its entire length there is probably not a quarter of a mile of straight track on it. It is a serpentine road in every respect and the curves are frequent and sharp. In hundreds of places the walls of granite are perpendicular and in many places the road bed is blasted out in the side of the walls of rock which overhang the track." He went on to proclaim, "Another such a feat of railroad engineering probably can not be found in the world, and there is probably no section of Colorado or of the whole country where such a varied and interesting lot of scenery can be found."[12]

Preserved rail bridge over Cimarron Creek

In the hopes of running the railroad through the rest of the Black Canyon, Palmer sent his top engineer Bryan Bryant on an inner canyon exploration. Bryant set off with a 12-man crew in December 1882 expecting to complete the survey in 20 days; he returned in 68. "Eight of the twelve-man crew left after a few days, terrified of the task in front of them. What the rest of the men saw was spectacular and had never been seen by another human." Bryant reported that the Black Canyon was impenetrable, and that it was impossible to build anything in its depths.[13]

Heeding Bryant's advice, Palmer decided to route the railroad south of the canyon and in March 1883, it completed its connection to Salt Lake City and for a brief period the canyon was on the main line of a transcontinental railroad system. While the railroad and early visitors used the canyon as a path to Utah and mines to the southwest, later visitors came to see the canyon as an opportunity for recreation and personal enjoyment.[14] Rudyard Kipling described his 1889 ride through the canyon in the following words: "We entered a gorge, remote from the sun, where the rocks were two thousand feet sheer, and where a rock splintered river roared and howled ten feet below a track which seemed to have been built on the simple principle of dropping miscellaneous dirt into the river and pinning a few rails a-top. There was a glory and a wonder and a mystery about the mad ride..."[15]

By 1890, an alternate route through Glenwood Springs had been completed and the route through the Black Canyon, being more difficult to operate, lost importance for through trains. However, local rail traffic continued over the "Black Canyon Line" until the route was finally abandoned in the early 1950s.[16][17] Today, various elements of the railroad have been preserved in the Cimarron area including a steel bridge in Cimarron Canyon.[18]

In 1901, the U.S. Geological Survey sent Abraham Lincoln Fellows and William Torrence into the canyon to look for a site to build a diversion tunnel bringing water to the Uncompahgre Valley, which was suffering from water shortages due to an influx of settlers into the area.[19] Torrence, a Montrose native and an expert mountaineer, joined four other men in a failed expedition to explore the canyon in September 1900 using two wooden boats. His experience proved invaluable on the second attempt in August 1901. Torrence and Fellows opted to bring a small specially made multi-chambered rubber raft with a lifeline all the way around it instead of the wooden boats that had doomed the previous journey. The two men entered the canyon on August 12 equipped with "hunting knives, two silk lifeline ropes, and rubber bags to encase their instruments." Torrence and Fellows each had backpacks weighing 35 pounds and the rubber raft turned out to be a great way to float their gear on the narrow river. After 10 days of climbing over rock falls, descending waterfalls, and swimming over 70 sections of the river, they emerged from their 30 mile run with a first recorded descent as well as a suitable tunnel site.[20][21][22][23][24]

Construction on the tunnel began 4 years later, and was fraught with difficulties right from the onset. "Working conditions at the tunnel were difficult due to the high levels of carbon dioxide, excessive temperatures, humidity, water, mud, shale, sand, and a fractured fault zone...It took the tunneling crew almost one year to bore through 2000 feet of water-filled rock. The tunnel was driven through granite, quartzite, gneiss, and shale as well as layers of sandstone, coal, and limestone. Work on the Gunnison Tunnel was first done manually and by candlelight. One miner would hold the drill and rotate it while the second miner would use a sledgehammer to drive the drill into the rock. This work required strong, hard-working men. In spite of good pay and fringe benefits, most disliked the dangerous underground conditions and stayed an average of only 2 weeks." 26 men were killed during the 4 year undertaking. The tunnel was finally completed in 1909, stretching a distance of 5.8 miles and costing nearly 3 million dollars. At the time, the Gunnison Tunnel held the honor of being the world's longest irrigation tunnel. On September 23, President William Howard Taft dedicated the tunnel in Montrose.[25] The East Portal of the Gunnison Tunnel is accessible via East Portal Road which is on the South Rim of the canyon. Although the tunnel itself is not visible, the diversion dam can be seen from the campground.[26]

Park Headquarters, South Rim

The Black Canyon of the Gunnison was established as a national monument on March 2, 1933, and was redesignated a national park on October 21, 1999.[27] During 1933-35, the Civilian Conservation Corps built the North Rim Road to design by the National Park Service. This includes five miles of roadway and five overlooks; it is listed on the U.S. National Register of Historic Places as a historic district.[28]

About half of the park, 15,599 acres (63.13 km²), was designated a wilderness area in 1976.[29]