They dragged the keel boats and the mackinaws up the river, living on only dried meat and occasional fresh game.  They built a dozen trading forts along the length of the Upper Missouri during the years of 1831 to 1846 using only the simplest of tools.  They took the work and the hardship as it came, doing what they knew how to do, living as they knew how to live.

In the spring of 1846 the American Fur Company's agent at Fort Lewis, Alexander Culbertson, received a request from the Blackfeet to relocate the fort to the north side of the Missouri River. A broad grassy river bottom on the north side a few miles down river was selected and work began on the site of Fort Benton, the last fur trading fort on the Upper Missouri.  Fort Lewis' log buildings, walls and bastions were dismantled and floated to their new site.  By the spring of 1847 the last structures were rafted down the Missouri to became a part of the new trading post.  But Alexander Culbertson was not satisfied with his fort.  While at Fort Laramie he had seen the adobe buildings of the Southwest, and he felt adobe would offer more protection against the Upper Missouri's extreme weather than logs could.  Reconstruction of the fort using adobe bricks made of Missouri River clay began in the fall of 1848.  A two story dwelling for Major Culbertson was the first building completed.  Reconstruction was completed in 1860 when the trade store was rebuilt.

Like all the other trading posts of this region, Fort Benton was built in a quadrangle.   It was over 150 feet square exclusive of the 20 foot square two story Bastions or Blockhouses.  Portholes in the bastion walls for both cannon and riflemen commanded a shooting range on all four sides of the fort.  An adobe wall fourteen feet high connected all the buildings and enclosed the quadrangle. Buildings contained within the compound were the Agents' Quarters, the Engages' Quarters, the Trade Store and attached Warehouse-Storage building, the Blacksmith and Carpenter's Shop, the Kitchen, and the Barn.  A large timbered gate was located between the northeast bastion and the long warehouse.  A smaller gate admitted Indians, a few at a time, into an enclosure, a part of the trade store, where they could pass their pelts and receive goods in return -- at first some colored cloth or a string of beads for a beaver skin and later for a buffalo hide.

By 1865 the fur and robe trade was dead and the American Fur Company sold the fort to the military, ending its control of the Upper Missouri.  The fort had already begun to crumble when the military finally occupied it in 1869.  In 1875 the military abandoned the fort and for the next few years private families occupied its buildings.   Abandoned by all but the rats in 1881, the buildings continued to deteriorate and gradually collapsed.  Lieut. James H. Bradley who served at Fort Benton during the military occupation wrote in his journals "Gradually the wild country became to tame for the great fur traders.  The forts passed into the hands of the federal troops and the heroic role of the trapper and trader had been played.  He had found the trails which the settler followed. He had explored and named the lakes and the streams.  He had learned how to deal with the tribes so that their full fury was never unleashed upon the settlers.  He released a primitive source of wealth which built nations."

By 1900 only the crumbling northeast bastion remained of the most important fur post during the final years of the fur and robe trade.  In 1908 the Daughters of the American Revolution with donated funds and $1500 received from the Montana Legislature took it upon themselves to rescue this last remaining structure.  One of the oldest buildings in Montana is still standing today because of their efforts.