Sunday, August 14, 2016

Fort Union Trading Post National Historic Site

About a week ago I returned from Fort Union Trading Post National Historic Site, where I'd been dispatched on official business. Fort Union Trading Post NHS, not to be confused with Fort Union National Monument in New Mexico, is located just north of the Missouri River on the North Dakota–Montana border. The reconstructed trading post itself is in North Dakota, but just barely; you can park in Montana and walk to it in less than five minutes (and gain an hour doing so, because you're also crossing time zones. Watch out for time paradoxes!). The fort was established for the American Fur Company in 1828 and lasted until 1867, after the fur boom years had passed. When people talk about forts in the American West, they often conjure images of cavalry, cattle, covered wagons, warfare with Native Americans, and so on. Fort Union, although it has appropriate prickly pears and yucca, was not a military post, although some of its building materials did become part of the Army's Fort Buford just down the river. Instead, as the name makes plain, it was a trading post, where Native Americans from many tribes traded furs for goods. At the time, it was ideally situated right above the Missouri River, but rivers get restless and this one has moved well south on its floodplain. Fort Union itself is not a hotspot for finding fossils, although an occasional inch-scale fragment of petrified wood can be seen, not an unusual thing for North Dakota (and if you do visit the fort and see such a piece, please don't take it!). However, the fort has a place in the historic development of North American paleontology.

Most of Fort Union from just outside the southwest bastion
This all goes back to a fortunate convergence of geography and company policy.  The AFC, via the Chouteau family, was noted for its support of artists and scientists, including such notables as John James Audubon, George Catlin, Joseph Nicollet, and Prince Maximilian of Weid, and encouraged their activities (Chaky 2015). Alexander Culbertson, the bourgeois (or manager) of Fort Union from 1837 to 1847, at times traveled from Fort Union to Fort John on the Laramie River, via Fort Pierre in what is now South Dakota. Fort John is better known as Fort Laramie, which incidentally also did not start out as an Army post, but as a fur trading post. It only became an Army post in 1849. The Fort Pierre–Fort John route took him across the Mauvaises Terres (spelled various ways in various sources), today better known as the White River Badlands. On these trips, he would occasionally collect fossils. He is probably the source of the first scientifically reported Badlands fossil, a jaw fragment which became named Paleotherium prouti and which is now known to have belonged to a brontothere (Wischmann 2000). He definitely provided the fossils that Joseph Leidy described as Poebrotherium wilsonii (a camel) and Merycoidodon culbertsonii (an oreodont, in fact "the" oreodont) (Chaky 2015), kick-starting vertebrate paleontology in the Badlands and west of the Mississippi in general. Early press on these finds in the late 1840s attracted other geologists. Among them was David Dale Owen, at that time working on a survey of Iowa, Minnesota, and Wisconsin. He dispatched subordinate John Evans to the Badlands in 1849. Evans returned with another load of vertebrate fossils which was sent to Leidy, whose descriptions of the bones makes up a chapter in Owen's massive 1852 survey publication. The AFC got into the act by sending Alexander's brother Thaddeus with another group in 1850 to make additional collections. In 1853 there was even an early foretaste of the Bone Wars when a government railroad survey crew including Evans butted heads with Ferdinand Vandeveer Hayden and Fielding Bradford Meek (Chaky 2015).

Another lasting trace of the early paleontological work in the area is the name of a rock unit that is commonly exposed in western North Dakota and eastern Montana: the Fort Union Group (North Dakota Geological Survey name) or Fort Union Formation (Montana Bureau of Mines and Geology name). This Paleocene-age sedimentary unit is the source of the Wannagan Creek fossils which can be viewed at the Science Museum of Minnesota, and makes the picturesque badlands of Theodore Roosevelt National Park and Little Missouri National Grassland. It does not appear to be exposed within Fort Union Trading Post NHS, although it is exposed in the uplands just beyond. Hayden used Fort Union as his base of operations in 1854 and early 1855, making collections of nonmarine mollusks from sites around the fort (Hartman 1999; Chaky 2015).

The Fort Union Group in the North Unit of Theodore Roosevelt NP


Chaky, D. 2015. Fossils and the fur trade: the Chouteaus as patrons of paleontology. We Proceeded On 41(2):12–23.

Hartman, J. H. 1999. Western exploration along the Missouri River and the first paleontological studies in the Williston Basin, North Dakota and Montana. Proceedings of the North Dakota Academy of Science 53:158–165.

Owen, D. D. 1852. Report of a geological survey of Wisconsin, Iowa, and Minnesota; and incidentally of a portion of Nebraska Territory. Lippincott, Grambo & Co., Philadelphia, PA. Available at (plates not included), (full plates) or

Wischmann, L. 2000. Frontier diplomats: Alexander Culbertson and Natoyist-Siksina' among the Blackfeet. University of Oklahoma Press, Norman, Oklahoma.

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