Fort Union Trading Post National Historic Site ⓘ

The Assiniboine tribe (pronounced uh-SIN-uh-boin) was the principal trading partner for Fort Union. In fact, the post was built on land in Assiniboine territory specifically at the tribe's request. Not surprisingly, then, the Assiniboine looked to Fort Union with protective eyes, helping to keep the post safe from occasional hostilities that might erupt among the tribes that came here to trade. To learn more about this Upper Missouri tribe, please see our Assiniboine page.

The Crow Indians were probably the second most common tribe at Fort Union, especially in the early years. The Crows' home was up the Yellowstone River and the south bank of the Missouri was considered the northern limit of their hunting grounds. Bands of Crow people were often found at Fort Union awaiting their turn to trade their buffalo robes, which were in high demand amongst the traders as Crow women were widely held to be the best tanners of prime winter buffalo cow hides.

The Crow are also a Siouan-speaking people, but their language is not mutually intelligible with the Sioux language. The Crow are widely held to be a splinter group of the Hidatsa, a riverine tribe covered below. The Crow and the Hidatsa were close allies and were culturally and linguistically similar.

The Blackfeet are often thought of as one tribe however they were actually three closely allied and related tribes, the Piegan, the Blood, and the Blackfoot. For many years the Blackfeet traded almost always with the Hudson's Bay Company of Canada, discouraging (often violently) attempts by American traders and trappers to enter their territory. However, after the construction of Fort Union Kenneth McKenzie made it one of his goals to win over the Blackfeet Indian trade to the American side. To effect this he sent Jaques Berger, a company employee who had lived among the Blackfeet, to bring them to Fort Union. Berger was successful and the Blackfeet began trading with the American Fur Company at Fort Union. Soon, the Company would build Fort McKenzie, and later Fort Benton, closer to Blackfeet territory. Even so, bands of Blackfeet would still occasionally show up at Fort Union to trade and visit with their friends.

The Blackfeet speak an Algonkian language and share some cultural similarities with other Algonkian tribes. For a time they were allied with the Atsina (Gros Ventre), a closely related group of the Arapaho Indians. They were also allied with the small Sarsi tribe of north-central Alberta, Canada.

Like the Blackfeet, the Plains Cree are a Algonkian speaking people. However their language and culture are very different to that of the Blackfeet. At one time the Cree people all dwelled in the forests of Eastern Canada and the United States. During the 1700s bands of the Cree began following the British and French fur traders westward onto the plains. These bands became known as the Plains Cree and adopted the general Plains culture of buffalo hunting and tipi dwelling.

Plains Cree and their close allies, the Plains Ojibwa, were often found at Fort Union, especially in the company of their other close ally, the Assiniboine. In the later years at Fort Union the Plains Cree may have been the second most common tribe present, surpassing the Crow.

The Plains Chippewa like their allies the Plains Cree, are an Algonkian speaking people. At one time they controlled most of the land around the Great Lakes, but war with other tribes and European settlers gradually forced them westward. By the 1700s many bands of Chippewa had entered modern day North Dakota and Saskatchewan, adopting the Plains lifestyle as they did so.

The Plains Chippewa (also known as the Ojibwa) frequently traveled with their allies, the Plains Cree and Assiniboine, and were thus often found trading at Fort Union.

Most likely the first "modern" Indian tribe to inhabit the modern-day state of North Dakota, the Mandan are a Siouan speaking people that arrived in the area in the 1400s or 1500s. The Mandan were an earthlodge dwelling people, living in semi-permanent villages and towns along the Missouri River and primarily using hide tipis only when hunting buffalo or otherwise traveling. The Mandan were an agricultural people, growing large gardens of corn, beans, squash, and tobacco.

The Mandan were well known to fur traders by the time Lewis and Clark arrived at their villages in 1804. The Mandan provided Lewis and Clark with important information about the Missouri River further upstream and allowed them to build a small fort for a winter camp near the villages, which the Captains named Fort Mandan in honor of their new friends.

Also a Siouan speaking group, the Hidatsa (the group from which the Crow split) moved westward into the Upper Missouri Region in the 1600s, encountering the Mandan and arriving prior to the fur traders. The Mandan and Hidatsa were closely allied and during their first meeting the Mandan called them Minitari or Crossing the river. However, their languages are different and they shared limited "Plains" culture traits.

The Hidatsa also provided some information to the Lewis and Clark Expedition, but were not as openly warm as the Mandan were. Whoever, it would be in the Awahtixa village where Lewis and Clark would find Sacagawea and Charboneau. The Hidatsa and Mandan could often be found at Fort Union until the American Fur Company eventually build Fort Clark, and later Fort Berthold, for their trade. In the late 1800s, after Fort Union was closed, a band of Hidatsa, tired of the reservation life and wars with their enemy the Lakota as well as inter-tribal politics, moved their village to the old Fort Union garden in order to be closer to Fort Buford a United States Army post. They would return back to Fort Berthold by the late 1880s.

The Arikara are a semi-sedentary tribe like the Mandans and Hidatsas, however they are more related to the Pawnee and speak a Caddoan language. They were living along the Missouri River in modern-day South Dakota the during the 1700s and had peaceful relationships as well as battles with the Mandan, Hidatsa, and some fur traders. The United States Army in 1823 attacked their main villages in retaliation for an Arikara attack on William H. Ashley's fur trade expedition which sources say began when two trappers crept in to the villages in the middle of the night to find female companionship after a couple of days of trading. After the battle with the United States Army 6th infantry, the Arikara temporarily adopted the nomadic Plains lifestyle. Eventually they returned to their sedentary lifestyle and by the 1830s were again living in villages along the Missouri.

Following the 1837 smallpox epidemic, which was particularly devastating to the Mandan, Hidatsa, and Arikara, the Arikara allied themselves with the Mandan and Hidatsa in 1862 and moved in with their former neighbors for equal protection from the Lakota. Today, these three tribes are known as the Three Affiliated Tribes.

The Sioux are made up of three large tribes that share a common language (with only slight dialect differences) and culture. The three divisions are the Dakota, the Nakota, and the Lakota (named here for their dialects). The Eastern Dakota lived mainly in Minnesota though some bands would venture further west onto the Plains following the 1862 Minnesota Uprising War. The Nakota, or Middle Sioux, consisted of the Yankton and Yanktonai, and dwelt in modern-day central North Dakota and eastern South Dakota. The Lakota, or Western Sioux (also known as the Teton Sioux), were the largest Sioux tribal group, made up of seven bands. These seven consisted of the Oglala, Brule, Hunkpapa, Minneconjou, Sans Arcs, Blackfeet (not to be confused with the Blackfeet tribe, above), and Two Kettle. The Lakota inhabited a vast area from the Missouri River west to the Bighorn Mountains and from the Platte River north into the extreme southern parts of the Canadian Plains.

The Lakota did not make an appearance at Fort Union until the 1840s and did not start showing up in large numbers until the late 1850s. By the time Fort Union closed in 1867 the Lakota had moved in in large numbers and taken the territory from the Assiniboine. It was primarily the Hunkpapa Lakota in the Fort Union vicinity, but family groups or individuals from most bands could be found from time to time in the area.

An 1864 black and white copper plate engraving of John Jacob Astor (FOUS 2818). NPS Photo.

In 1828, John Jacob Astor's American Fur Company established what would become its most renowned fur trade post near the confluence of the Missouri and Yellowstone Rivers. Although referred to as a fort, Fort Union was not a government or military installation; it was a privately owned commercial establishment created to engage in trade with the Northern Plains tribes. Built at the request of the Assiniboine Nation, Fort Union quickly became the most profitable fur trade post in the Upper Missouri region. The trading activities at Fort Union continued until 1867, fostering a diverse, peaceful, and productive social and cultural environment that contributed to its longevity as the longest-lasting fur trade post in the western United States.

From 1828 to 1867, many Upper Missouri tribes — Assiniboine , Crow, Plains Cree, Blackfeet, Plains Ojibwa, Mandan, Hidatsa, Arikara, Lakota and Dakota —traded buffalo hides, beaver pelts, and other furs for numerous goods imported from eight different countries. In exchange for furs that included grizzly bear pelts, bison hides, and smaller animal furs, tribal trading partners received manufactured goods such as calico cloth, firearms and ammunition, clothing, pipes, beads, and cooking supplies. On average, Fort Union received more than 25,000 buffalo robes and generated over $100,000 in merchandise sales each year.

Additionally, Fort Union served as a base of operations and storage facility for federal Indian agents before the national government established a permanent presence in the Trans-Mississippi West after the Civil War.

A lithographic print of "Fort Union on the Missouri" published circa 1843 (FOUS 2761). NPS Photo.

The American Indian and fur trades were not the only activities that contributed to Fort Union's lasting legacy. The American Fur Company and its successors regularly hosted notable visitors during the fur trade period. Artists and scientists such as George Catlin, Prince Maximilian of Wied, Karl Bodmer, and John James Audubon came to Fort Union to study and document the region's native peoples, wildlife, and landscapes. Their observations, captured in sketches, paintings, and journals, were shared with audiences in the East and abroad, making the area one of the most well-documented parts of the American West before photography became widespread.

By the 1860s, the Upper Missouri region had begun to undergo significant political and social changes. Following the establishment of the Dakota Territory in 1861, settlers migrated westward in increasing numbers. To protect the Missouri River—an essential transportation route to the Northern Plains—and the growing Euro-American settlements that had taken over the previously tribal-controlled Upper Missouri region, the U.S. Army built Fort Buford three miles east of Fort Union in 1866. The following year, in 1867, the Army purchased Fort Union from its last private owner, the Northwest Fur Company. Soldiers dismantled the fort’s palisades and bastions, repurposing the salvaged timber and stone for construction at the new Army post. In addition, passing riverboat crews scavenged wood from Fort Union for firewood to fuel the steam engines of the increasing number of steamboats on the Missouri River. Within a few years, little remained of what was once a dominant commercial hub in the Upper Missouri region.

A century later, after numerous attempts to preserve Fort Union's legacy, local citizens and historians initiated a sustained campaign to protect the historic site and rebuild the fort. Their efforts led to the National Park Service acquiring the site in 1966. Archaeological excavations began two years later and continued into the early 1970s. Today's Fort Union is a reconstruction based partly on the archaeological evidence gathered during those digs, as well as follow-up excavations completed between 1986 and 1988. Rebuilt to reflect its appearance in 1851, when the buffalo robe trade was at its peak, Fort Union serves as a vital venue for understanding the fort's role in shaping the land and culture of the Upper Missouri region and the Northern Great Plains.

The adoption of metal arrowheads, or projectile points, by the peoples of the Upper Missouri River is a prominent example of cultural change that is discussed at the fort today. Prior to European contact, the Assiniboine and other Northern Plains tribes crafted stone arrowheads using a technique called knapping, where they would chip flakes from a stone core with a harder rock. The three stone arrowheads shown in the top row of the image on the right were discovered by archaeologists at Fort Union and were made from Knife River flint, a strong and durable material quarried 250 river miles to the east of the post and traded upriver.

With the establishment of Fort Union, traders introduced the Upper Missouri River peoples to new materials, technologies, and supplies. As trading relationships expanded, the cultural exchange between the tribes and Euro-Americans intensified. The Assiniboine and neighboring tribes increasingly began to purchase and utilize easily made iron, brass, and copper projectile points, similar to the ones also shown in the image.

We invite you to explore this site further and discover the people , places , archaeological collections , and stories that illuminate the post's and the region's rich natural and cultural heritage. Detailed information about the fort's reconstruction and historic furnishings can be found on our Fort Union 50th Anniversary pages. We also invite you to help us preserve and share these resources and stories.

MAMMALS The most common mammals at Fort Union include white-tailed deer, coyote, red fox, ground squirrels, beaver, muskrat, desert cottontail, raccoon, porcupine, and prairie vole. BIRDS The site's location along a major flyway results in the seasonal passage of an array of migratory and non-migratory birds, including Canada geese and white pelicans. In the winter golden and bald eagles lay over and prey in the scattered open river waters. Smaller species include American Goldfinch, Lazuli Bunting, Black-Headed Grossbeak, and Pine Siskin. INSECTS Numerous insect species are recorded along the Missouri of which mosquitoes are historically the most nettlesome. In 1806, Captain Clark was to wait for Lewis at the confluence of the Missouri and Yellowstone, but moved several miles downstream to escape the "mosquitors". AMPHIBIANS Chorus frog, Leopard Frog, and Spadefoot Plains Toad use the river bottoms as breeding and feeding grounds, and are occasionally seen within the fort. REPTILES Garter snakes may be seen sunning in open areas or darting out of sight. Bull snakes are rarely seen, camoflaged in the prairie by day and hunting in mammal burrows by night.