The forts that bore Bartholomew Berthold's name lie somewhere beneath Lake Sakakawea, lost since the 1950s when the Garrison Dam drowned the Missouri River bottomlands. Berthold himself never saw them. He died in St. Louis in 1831, fourteen years before the American Fur Company named its upper Missouri outpost in his honor. The Italian immigrant had married into the Chouteau fur-trading dynasty, anglicized his name from Bertolla de Moncenigo, and built a mansion that would later serve as headquarters for pro-Confederate secessionists. His frontier namesakes would pass through fire and flood before vanishing beneath government-made waters.
The American Fur Company founded the original Fort Berthold in 1845 on the upper Missouri, initially calling it Fort James before renaming it the following year for the deceased St. Louis merchant who had once been part of their trading network. For seventeen years the post served as a hub for the fur trade that drove the regional economy, connecting Native trappers to eastern markets through a network of rivers and trails. Then came the Dakota War of 1862, when conflict between the United States and various Sioux bands spread across the northern Plains. The Sioux burned Fort Berthold to the ground. The American Fur Company needed a new location.
Four years before the first fort burned, trader Charles Larpenteur had built an independent post called Fort Atkinson on the Missouri south of present-day White Shield, North Dakota. When the American Fur Company lost their original facility, they purchased Larpenteur's fort and transferred the Berthold name to its new home. The U.S. Army soon took over, stationing a garrison and establishing a log camp outside the stockade to supply troops through the brutal winter of 1864-1865. The military presence lasted until 1867, when soldiers relocated to Fort Stevenson further down the river. What happened next would define the site's legacy for nearly a century.
When responsibility for Native American relations shifted from the War Department to the Department of the Interior, the second Fort Berthold found a new purpose. After 1868 it served as the Indian Agency for the Arikara, Hidatsa, and Mandan peoples, three distinct nations administered together on what became the Fort Berthold Indian Reservation. The fort also continued operating as a trading post until 1874, maintaining some connection to the commercial activity that had first brought Europeans to this stretch of river. For decades the tribes built lives in the fertile bottomlands along the Missouri, establishing towns, farms, and cemeteries in the valley that had sustained their ancestors.
The Garrison Dam changed everything. Completed in 1953, the massive earthen structure created Lake Sakakawea, one of the largest man-made reservoirs in the United States. The flooding claimed both fort sites, erasing any physical trace of the structures that had shaped regional history for over a century. But the dam took far more than abandoned military posts. The Arikara, Hidatsa, and Mandan peoples lost the most fertile portions of their reservation, the bottomlands where generations had farmed and built communities. Homes, towns, and cemeteries disappeared beneath the rising waters. The tribes were forced to relocate to higher ground, surrendering their ancestral lands to a reservoir named for the same Sacagawea who had once lived among them at the Knife River villages upstream.
Nothing visible survives of either Fort Berthold today. The waters of Lake Sakakawea cover both locations, their exact positions known only from historical records and old maps. The Fort Berthold Indian Reservation still exists, home to the Three Affiliated Tribes formed from the surviving Arikara, Hidatsa, and Mandan peoples. The name Berthold persists on the reservation, the agency, and countless official documents, a permanent reminder of an Italian immigrant who never traveled west of St. Louis but whose name would become synonymous with both the frontier fur trade and one of the most significant forced relocations of the twentieth century.
The former fort sites lie beneath Lake Sakakawea at approximately 47.51N, 101.81W in central-northwest North Dakota. The massive reservoir is unmistakable from altitude, stretching roughly 180 miles along the Missouri River valley. Best viewed at 3,000-5,000 feet AGL where the full extent of the flooding and the irregular shoreline are visible. The Garrison Dam is clearly identifiable at the lake's southern end. Nearest airports: Mercer County Regional (K2R2) approximately 15 nm south, or Minot International (KMOT) about 45 nm north. The lake itself serves as an excellent visual navigation reference across this sparsely populated region.