From the highway between Dubois and Crowheart, the Wind River Range is a long wall on the southwestern sky, and on a clear day its high crest still shows white in August. That white is ice. The Wind Rivers hold the largest concentration of glaciers in the American Rockies, some sixty-three of them, most clustered around Gannett Peak, at 13,804 feet the highest summit in Wyoming.
The biggest ice in the Rockies
Gannett Glacier, on the peak's north and east flanks, is the largest glacier in the Rocky Mountains of the United States, and Dinwoody Glacier beside it has ranked among the four largest. Both drain to Dinwoody Creek, which carries meltwater from more glacier ice than any other single headwater stream in the lower forty-eight. The creek runs down through the Wind River Reservation to the Wind River, and from there to the Bighorn, the Yellowstone, the Missouri and the Mississippi. The range straddles the Continental Divide, and its snow and ice also feed the Green, bound for the Colorado, and the Snake, bound for the Columbia. Wyoming's state water plan estimates the range's glaciers yield about 57,000 acre-feet of meltwater a year, most of it from July into October, after the snowpack is gone and the rivers are low.
The range lent its name to the ice ages themselves, at least in this part of the world. In 1915 the geologist Eliot Blackwelder worked out a sequence of glaciations from the moraines on the range's flanks and named them for the places he found them; the last, the Pinedale, is still the standard name for the most recent glaciation across the Rocky Mountains. The glaciers hanging below Gannett now are far smaller than those ice-age valley glaciers. They reached their recent size during the cool centuries known as the Little Ice Age and have been retreating since it ended in the 1800s.
A measured retreat
Scientists have watched that retreat for seventy years. Mark Meier photographed more than twenty of the range's glaciers in the 1950s and measured Dinwoody losing mass each year from 1958 to 1961. A 1989 study using repeat photographs and radar found that Dinwoody had thinned by an average of about seventy-six feet between 1958 and 1983. Satellite work comparing 1985 and 2005 found that the smaller glaciers had lost an average of 43 percent of their surface area and the larger ones 22 percent. A 2025 study taking the record back to 1968 measured a loss of about a fifth of the glacier area across the range through 2019, and found the thinning had sped up after 2000 as more of the high-country precipitation fell as rain.
What that means downstream is argued. Some studies put glacier melt at only 1 to 12 percent of the yearly flow in the watersheds below, small beside the snowpack, and Wyoming's water managers have said as much. But the melt comes in late summer, when little else does, and it runs through reservation land on its way to the farms and ranches below. The glaciers lie at the end of long trails into the Fitzpatrick Wilderness or up the reservation's backcountry, which needs a tribal permit. Most travelers see them only as that white line on the crest. It is thinner than it was.