Gannett Peak in the Wind River Range is Wyoming’s highest mountain, at about 4,209 m (13,810 ft), and it heads a state of separate ranges rising out of high, dry basins. The Teton Range, crowned by the Grand Teton at 4,199 m (13,775 ft), stands in the northwest beside the Absaroka, Gros Ventre and Wind River ranges; the Bighorn Mountains, topped by Cloud Peak at 4,015 m (13,171 ft), rise in the north centre; the Laramie Mountains, the Snowy Range and the Sierra Madre cross the south; and the Black Hills reach in from the northeast. Between them lie basins such as the Bighorn, the Great Divide and the Powder River. Wyoming covers 253,340 km² (97,814 sq mi), and its mean elevation of about 2,040 m (6,700 ft) is the second highest of any state. Even its lowest point, where the Belle Fourche River leaves for South Dakota, sits at 945 m (3,099 ft). Walking down from the top, feature by feature, shows how the state is put together.
Gannett Peak, 4,209 m on the Continental Divide
Gannett Peak straddles the Continental Divide on the boundary of Fremont and Sublette counties, and its slopes fall into both the Bridger-Teton and Shoshone national forests. It is the highest ground for 467 km in any direction and the highest point in the Rocky Mountains outside Colorado. Named in 1906 for the geographer Henry Gannett, it was first climbed in 1922 by Arthur Tate and Floyd Stahlnaker, and its remoteness still makes it one of the hardest state high points to reach.
The peak’s northern slopes carry the Gannett Glacier, about 363 ha (896 acres) and likely the largest single glacier in the American Rockies, and the Dinwoody and Gooseneck glaciers lie on its southeast side. Gannett is only the summit of a long wall: the Wind River Range runs about 160 km northwest to southeast with the Divide along its crest, and after the Grand Teton the next 19 highest peaks in the state are all in the “Winds”, including Fremont Peak at 4,191 m. More than 40 other named peaks there top 3,962 m (13,000 ft). Archaeologists have studied Sheepeater Shoshone villages as high as 3,000 m in the range, one of them, “High Rise”, with 60 lodges.
The Grand Teton and the Teton Fault
Just 10 m lower than Gannett, the Grand Teton is by far the more recognisable peak, because it rises abruptly from the flat floor of Jackson Hole. The Teton Range is a block of crust tilted up along the Teton Fault. Between six and nine million years ago, stretching of the crust began moving the fault: the western block rose into the range, and the eastern block dropped to form Jackson Hole, making the Tetons the youngest range in the Rocky Mountains. The valley floor averages about 2,100 m (6,800 ft), so the Grand Teton towers roughly 2,100 m above it.
The range is only about 64 km long, but its central Cathedral Group packs in the Grand Teton, Mount Owen (3,940 m), Middle Teton (3,903 m) and Teewinot (3,757 m). The rock is young in form and ancient in substance: gneiss that began as sediment about 2.5 billion years ago, shot through with granite and with black diabase dikes visible on the faces of Mount Moran and the Grand Teton. Several periods of glaciation then carved the peaks into their present shapes, and Teton Glacier still sits below the Grand Teton’s north face. Grand Teton National Park was established in 1929.
Cloud Peak and Francs Peak in the North
In the north of the state, two ranges frame the Bighorn Basin. On the west side, the Absaroka Range reaches 4,011 m (13,158 ft) at Francs Peak in the Washakie Wilderness, the high point of Park County, named for the cattle baron Otto Franc. On the east, the Bighorn Mountains run about 320 km north into Montana as a spur of the Rockies pushing out onto the Great Plains. They were uplifted in the Laramide orogeny beginning about 70 million years ago, carrying more than 2,700 m of fossil-rich sedimentary layers on their flanks.
Cloud Peak, at 4,015 m (13,171 ft), crowns the 765 km² Cloud Peak Wilderness. Because it rises alone above an isolated range, its topographic prominence of 2,157 m is the greatest in Wyoming, one foot more than Gannett Peak’s. A deep cirque on its northeast side holds Cloud Peak Glacier, the last active glacier in the Bighorns.
Medicine Bow Peak and the Southern Ranges
Southern Wyoming is lower, but not flat. About 56 km west of Laramie, Medicine Bow Peak rises to 3,663 m (12,018 ft), the highest summit of the Snowy Range, a subrange of the Medicine Bow Mountains and the highest point in the southern half of the state. Wyoming Highway 130, the Snowy Range Road, climbs over the Medicine Bow Mountains west of Laramie as a designated scenic byway. To the east, the Laramie Mountains run from northern Colorado between Cheyenne and Laramie and north toward Casper, the last of the Front Range line; the gap between them and the Bighorns carried the Oregon Trail, the Mormon Trail and the Pony Express. To the west, the Sierra Madre carries the Continental Divide along its high points south of the Great Divide Basin; Wyoming Highway 70 crosses the Divide there at Battle Pass, 3,022 m (9,915 ft).
Yellowstone Lake on the Caldera Plateau
The Yellowstone Plateau in the northwest corner is a different kind of high ground, built by volcanism rather than faulting or folding. Yellowstone National Park, established in 1872 as the first national park in the United States, covers 8,983 km², about 96 percent of it in Wyoming. Its volcanic field began erupting 2.15 million years ago, and the most recent supereruption, about 631,000 years ago, produced the Lava Creek Tuff and collapsed the present Yellowstone Caldera. The last known magmatic eruption was about 70,000 years ago, but the heat below still drives the park’s geysers and hot springs.
Yellowstone Lake, at 2,357 m (7,732 ft), is the largest body of water in Wyoming and the largest freshwater lake above 2,100 m in North America. It covers about 350 km², has 180 km of shoreline, and is at least 120 m deep in places. Ice nearly a metre thick covers it from early December until late May or June, except over shallow hot springs.
South Pass and the Great Divide Basin
At the southern end of the Wind River Range the mountains give out onto a broad, open upland about 56 km wide. South Pass, at about 2,259 m (7,412 ft), is the lowest point on the Continental Divide between the Central and Southern Rockies. The first recorded crossing was made on 22 October 1812 by Robert Stuart and six companions of John Jacob Astor’s Pacific Fur Company, returning east from Astoria, and it became the gateway of the Oregon, California and Mormon trails, a National Historic Landmark since 1961.
South of the pass lies the Great Divide Basin, in the Red Desert, an endorheic basin beside the Continental Divide from which no water drains to any ocean. Rain that falls there stays in the basin or evaporates. Its aridity and salty flats pushed the Oregon Trail north over South Pass and the Overland Trail south over Bridger Pass, though the Union Pacific railroad later ran straight across the basin’s southern part.
Devils Tower Above the Belle Fourche
In the far northeast, near Hulett and Sundance in Crook County, Devils Tower rises from the pine and grassland beside the Belle Fourche River. The laccolithic butte of igneous rock stands 264 m (867 ft) from base to summit and 386 m above the river, with its top at 1,558 m (5,112 ft). Its Lakota name, Matȟó Thípila, means Bear Lodge. On 24 September 1906, Theodore Roosevelt made it the first national monument in the United States.
The Powder River Basin and Wyoming’s Lowest Point at 945 m
The Belle Fourche itself rises in southern Campbell County, in the Powder River Basin, a structural basin about 400 km long and 160 km wide that reaches north into southeastern Montana. The basin’s rolling semi-arid grasslands, once hunting grounds of the Oglala Lakota, sit on enormous coal seams: in 2007 the region produced 396 million tonnes of coal, more than twice the output of West Virginia. Gillette and Sheridan are its main towns.
From there the river flows northeast past Moorcroft, curls around the north side of the Bear Lodge Mountains past Devils Tower, and crosses into South Dakota. That crossing, at 945 m (3,099 ft), is the lowest ground in Wyoming and the second-highest low point of any state. Beyond it the Belle Fourche joins the Cheyenne River and, through the Missouri, the Mississippi, carrying water that fell on Wyoming’s plains all the way to the Gulf of Mexico.
From Gannett’s glacier to the Belle Fourche, the descent is about 3,260 m. For the wider range these peaks belong to, read our Rocky Mountains guide; for the volcano under the plateau, the geography of the Yellowstone supervolcano; and for the monolith at the bottom of the climb, the Devils Tower guide, or step back to the whole state in our Wyoming geography guide.