Pumpkin Buttes

Pumpkin Buttes and Uranium Fever

These buttes contain uranium that was likely created from the ash of volcanic eruptions some 50 million years ago. This is the site where in 1951 Dr. J.D. Love first discovered uranium in a Wyoming sedimentary basin. Love’s discovery led to uranium fever: Prospectors and ranchers postured for potential stakes. What historian T.A. Larson calls “the complex pattern of rights to land and minerals” in Wyoming led to confusion in all directions.

Dr. J.D. Love
Dr. J.D. Love, USGS. [Credit: Wyoming Geological Association]
Pumpkin Buttes and Uranium Fever, Wyoming's Cultural Geology Guide

Uranium Fever

Prospectors vs Ranchers
Prospectors vs Ranchers. [Credit: Denver Public Library]

Uranium has a long history in Wyoming, both in terms of its geological significance and its importance for society. In 1951, prolific geologist J.D. Love (USGS) discovered uranium at Pumpkin Buttes, in Campbell County. This ultimately led to uranium fever: Where ranchers and prospectors postured for potential stakes.

Prospectors prepared to stake claims. Ranchers, who owned the surface rights but not the minerals below, worried that all the people “rushing” for uranium would damage their lands. So the ranchers formed the Pumpkin Buttes Mining District. Under its terms, instead of filing claims with the county clerk, prospectors were required to file with the district, which had set aside more than 46,000 acres. In addition, those filing claims also promised to pay those who owned the surface rights a royalty on production.

The situation become so intense then Gov. Milward Simpson called in the National Guard to keep the peace. Ultimately, the Wyoming Supreme Court declared the Pumpkin Buttes Mining District illegal...so goes the history.

The Cold War: The Atomic Age

Pumpkin Buttes
Pumpkin Buttes, Campbell County, Wyo. [Credit: Chamois Andersen, WSGS, 2015]

In 1948, with tensions increasing between the United States and the Soviet Union at the start of the Cold War, the Atomic Energy Commission (AEC) issued a series of circulars providing for the procurement of uranium ores, setting minimum prices, bonuses for the discovery of new deposits, and other incentives for high-grade ores, haulage allowances, etc. With such payoffs, prospectors began scouring Wyoming for uranium ore.

Around the same time, uranium was discovered in 1949 in the Black Hills of Crook County. Also around that time, USGS geologist J.D. Love was pursuing the locations of uranium ore with his geologic research. He took to the air to conduct an aerial check of uranium in the Pumpkin Buttes portion of the Powder River Basin in southern Campbell County. Along with his colleagues, he conducted on-the-ground fieldwork to confirm what he had noted as uranium “hot spots.”

Prior to the 1950s, geologists believed that uranium deposits originated from hydrothermal activity. But U.S. Geological Survey geologists Denson, Bachman and Zeller hypothesized that uranium came from thick volcanic ash beds that covered Wyoming’s landmass beginning more than 50 million years ago. The beds were laid down by eruptions of ash from numerous volcanoes in the western United States, including some in the mountains that now make up the Absaroka Range in northwestern Wyoming.

Love, who was researching this volcanic ash theory, decided it was time to see if it would produce results. In 1951, he was the first to discover uranium in a Wyoming sedimentary basin at Pumpkin Buttes. The flanks of Pumpkin Buttes indeed had very impressive concentrations of uranium. The find was important geologically as it appeared to verify the hypothesis of ash-sourced uranium deposits. Now it appeared that uranium could possibly exist in nearly all parts of the state.

Since then, uranium has been discovered in porous sedimentary rocks in the Powder River, Great Divide, Wind River, and Shirley basins. In addition, there are significant uranium deposits in the western Black Hills area in northeastern Wyoming, the Little Mountain area of the northern Bighorn Range, and the eastern Greater Green River Basin. As a result of Love's and other discoveries, Wyoming is home to the largest uranium ore deposits in the United States.

Pumpkin Buttes

There are many stories about just how Pumpkin Buttes received its name. It may have been because of the shape of the buttes and color resembling pumpkins. They were also called Wa-ga-mu Paha (Gourd Hills) by Sioux Indians, named because of a tribal ceremony held there in which gourds were rattled.

It has also been speculated the name was derived from the pumpkin-sized iron concretions found below the buttes that were likely processed for uranium. Another theory is Jim Bridger named the buttes after wild pumpkins growing there. One thing is for sure, it is the site where in 1951 famed geologist J.D. Love first discovered uranium in a Wyoming sedimentary basin.

The history books also note that the four large, flat-topped buttes were used as landmarks by early travelers and as a hideout by Big Nose George Parrot and his gang. Big Nose George was finally hanged by vigilantes at Rawlins, after he tried to wreck and rob a Union Pacific train by pulling the spikes from the rails. A section boss discovered some loose rails and flagged the train down. The gang fled to Montana, where Big Nose George was finally caught.

Iron concretions, shaped like pumpkins
These iron concretions, shaped like pumpkins and once found at the base of the buttes, may be how Pumpkin Buttes received their name. [Credit: Darby Hand]


Amundson, Michael A., 2002, Yellowcake towns: Uranium mining communities in the American West: Boulder University Press of Colorado, p. 17-49.

Chenoweth, W.L., 1991, A summary of uranium production in Wyoming: Wyoming Geological Association 42 Annual Field Conference, p. 169-179.

Larson, T.A., 1978, History of Wyoming (2nd ed.): Lincoln, University of Nebraska Press, p. 514-517.

Urbanek, Mae, 1998, Wyoming Place Names: Missoula, Mountain Press Publishing Company (reprint), 233 p.