Gratiot County (/ˈɡræʃɪt/) is a county located in the U.S. state of Michigan. As of the 2010 census, the population was 42,476. The county seat is Ithaca, although its most populous city is Alma.Gratiot County comprises the Alma, MI Micropolitan Statistical Area, which is also included in the Mount Pleasant-Alma, MI Combined Statistical Area.The Gratiot County Courthouse was built in the classical revival style by Claire Allen, a prominent southern Michigan architect.