 The county was founded in 1829, and was organized in 1831, before Michigan was accepted into the Union as a state.When Michigan Territory was established in 1805, the area of present Berrien County was included in the boundary of Wayne County.About 1780, New Jersey resident William Burnett established a trading post at the mouth of the St. Joseph River (present-day site of St. Joseph) to serve indigenous peoples and French Canadian residents.