Fort Union Trading Post Historic Structures Report (Part II) Historical Data Section

When the dwellings caught on fire in 1833, McKenzie decided that being without a proper powder magazine was simply too dangerous. As a result, Denig (1843) was able to describe the new magazine as being

perhaps the best piece of work as regards strength and security, that could be devised for a fort like this. The dimensions are 25 by 18 ft.; it is built out of stone, which is a variety of limestone with a considerable quantity of sand in its composition. The walls are 4 ft. thick at the base, and increasing with the curve of the arch become gradually thicker as they rise, so that near the top they are about 6 ft. in thickness. The inside presents a complete semicircular arch, which is covered on the top with stones and gravel to a depth of 18 inches. The whole is covered with a shingle roof through which fire may burn yet with no danger to the powder within. There are two doors, one on the outside, the other a few feet within; the outer one is covered with tin.

Prince Maximilian (1833) described it as very handsome, of hewn stone, and capable of containing 50,000 pounds of powder. The location of the quarry from which McKenzie hauled the stone by cart, is unknown. It apparently was not very far from the fort; Audubon contemplated riding out to visit it but changed his mind (1843). Larpenteur's diary shows the magazine still stood in 1865.

According to Kurz (1851) the magazine was located at the rear of the warehouse. If this should mean at the north end of the store range, then it is the building that appears in Point's and Kurz' sketches, located to the east of the bourgeois' house and to the north of the store. This structure had an ordinary gable roof and its walls appear to have been whitewashed.