Hypolite Dupuis was born in Canada in 1807 at La Prairie de la Madeleine, near present-day Montreal.
Little is known of his early life, but by 1831 Dupuis moved to the region that would become Minnesota and worked for the American Fur Company (AFC) at Joseph Renville’s Lac qui Parle trading post. While there, Dupuis married Renville’s daughter, Angelique, in 1836. Dupuis was known to speak several languages, including French, English, and Dakota, which was likely helpful to him in his career.
It is uncertain when Dupuis arrived at Mendota. An 1840 census of Clayton Co., Iowa (of which Mendota was a part at the time), lists his name, but an 1868 newspaper article states Dupuis’s arrival as being in 1842 when he began working as a clerk for Henry Sibley at his Mendota headquarters. Throughout the 1840s and 1850s Dupuis and his wife lived in a log cabin situated on Sibley’s property, and their family grew to include seven children. While in Mendota the Dupuis family also raised Louise Allard, an orphaned girl identified as of “mixed-blood" ancestry. This illustrates the multi-cultural environment that was Mendota in the early 1800s.
While working for the AFC, Dupuis likely managed the affairs of the company store while Sibley was absent. However, by the 1850s the fur trade had largely died out in the region, and Sibley and Dupuis closed out their fur business in 1853. The following year Dupuis built a red brick house for his family and partnered with G. S. Whitman to operate a general store until it closed as a result of the financial panic of 1857. The house is part of the Sibley Historic Site.
Throughout the 1850s, Dupuis remained active in the Mendota community, serving as county treasurer (1854), the justice of the peace (1855), as well as the Mendota postmaster (1854-1863). In 1871 Dupuis sold his brick home to Timothy Fee, and moved to the Devil’s Lake Reservation in North Dakota to work as storekeeper for the Fort Totten Indian Agency. The Indian Agent for the reservation, William H. Forbes, was also a former employee of Henry Sibley.