Midland County is a county located in the U.S. state of Michigan. As of the 2010 census, the population was 83,629. The county seat is Midland. The county's name is due to its closeness to the geographical Lower Peninsula's geographical center. It was set off in 1831. Organization did not take place until 1850, and that 1850 organization "was never implemented:" It was not until 1855 that the county was effectively organized.