Branch County is a county in the U.S. state of Michigan. As of the 2010 census, the population was 45,248. The county seat is Coldwater. As one of the “cabinet counties” it was named for the U.S. Secretary of the Navy John Branch under President Andrew Jackson. The county was founded in 1829 and organized in 1833. Branch County comprises the Coldwater, MI Micropolitan Statistical Area.