Jules DeMun (1782–1843) was a 19th-century French-American fur trader. A well-educated and articulate French aristocrat, he was born in Port-au-Prince, Saint-Domingue and was educated in France. As a young man, he was displaced from his social position by the French Revolution, and he and his family fled to England. He emigrated to the United States in 1809 and arrived in St. Louis, Missouri in 1812.
After marrying into a fur trading family, DeMun joined the trade but had little natural skill. An early visit to the upper Arkansas River however caused him to consider the American Southwest's potential as a fur trading center. After learning of efforts in the Southwest by American trader, Joseph Philbert, DeMun and August Chouteau gathered a company and set off to New Mexico. Initially well received, they did some successful trapping and wintered in Taos, New Mexico. In early 1816, the company sought formal permission from the Spanish governor of New Mexico to trap and trade in the Spanish province. They were given permission to work in a limited area, but faced opposition from local Indian tribes.
In the winter of 1816–1817, DeMun and his company were formally detained near the village of Rio Colorado. In response to their letter appealing their detention, the Governor in Santa Fe ordered the company to leave Spanish territory. This sudden opposition may have been due to confusion and contention over boundaries involved in the Louisiana Purchase. DeMun's dogged persistence in seeking to negotiate in good faith for trapping rights in the area, and for the right to take their furs to St. Louis for sale, eventually ended in a short imprisonment and Spanish confiscation of all of the company's goods and furs.
DeMun never returned to the fur trade. After a checkered employment history in Cuba and Wisconsin, he was appointed secretary and translator to the U.S. Board of Commissioners adjusting titles of French and Spanish land grants in Missouri. He later became registrar of the United States Land Office at St. Louis. In 1842, he was elected St. Louis County Recorder of Deeds. (Hafen, p. 8-18)
In 1986 The site of the Demun's trading post was discovered and excavated by the University of Wisconsin. It was located on a bluff above the Sugar river near Monroe, Wisconsin. Fire Steels, ceramics, a clasp knife, and parts of a trap were found there. Charred logs found at the perimeter of the cabin indicate it was probably burned in The Black Hawk War (April 1832.)