They are just past South Pass, and are two flat-topped summits plus a smaller, conical one. For travelers on the Oregon Trail, the buttes were on the horizon for a day's travel, perhaps more. This was as they crossed Rock Creek, then Willow Creek, and, for the last time, the Sweetwater River.[1]
Pioneers on the trails used physically descriptive names for the buttes: "Table Rock," or "Table Rocks."[2]
Currently, they are in a remote area and can be difficult to get to.[1] From the top of a butte one can see for miles, including to the north the Wind River Range, and to the southwest the Uinta Mountains.[3]
They rise about 1,500 feet (460m) from the plain and are flat-topped.[4]
As the Oregon Buttes are just pass South Pass over the Rocky Mountains, to pioneers on the Oregon Trail they signified the entrance to the Oregon Territory.[2] In 1843, Theodore Talbot wrote "Today we set foot in the Oregon Territory, the land of promise." But hardships already experienced made him feel cautious, and probably thinking of recent hard travel, he added, "As of yet it only promises an increased supply of sage and sand." Joseph Warren Wood wrote "We are now in Oregon,"[4] In general, travelers on the Oregon Trail considered Oregon Buttes as marking the trail's halfway point. Pioneers also felt they had entered the Pacific Watershed.[8]
The buttes consist of soil layers and rocks from the Wasatch Formation (from lower to middle Eocene). This unit consists of variegated red, purple, and green mudstones and sandstones deposited by ancient river systems. This is followed by the Laney Member of the Green River Formation (middle Eocene). These are the remnants of Lake Gosiute, a massive prehistoric lake that once covered the Red Desert. Finally, the Bridger Formation (middle Eocene), which is famous for its mammalian fossils, similar to Fossil Butte near Kemmerer. The summits are capped by the Arikaree Formation (lower Miocene), which includes tuffaceous sandstones and conglomerates that have protected the softer underlying layers from erosion.[9][10][11] The Bridger and Green River formations have yielded primitive mammals, including early primates and rhinoceros-like herbivores. Specifically, fossils of the genus Lambdotherium have been documented in the area.[12]
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