 While trading in Mexico, DeMun was imprisoned alongside A. P. Chouteau for 48 days in Santa Fe, leading the group to file a claim against the Mexican government for confiscated goods worth $30,000.Payment for the claim was not obtained until 1851, through an act of Congress.In 1817, DeMun opened a trading business with Auguste Pierre Chouteau in St. Louis, known as A. P. Chouteau, DeMun & Co., or Chouteau, DeMun & Sarpy.