Isabella County is a county located in the state of Michigan. As of the 2010 Census, the population was 70,311. Its county seat is Mt. Pleasant.
The area was known as Ojibiway Besse, meaning "the place of the Chippewa. It was set off as a county in 1831, and county government organized in 1859. It was named after Queen Isabella I of Castile, based on a suggestion by Henry Schoolcraft. Isabella County comprises the Mount Pleasant, MI Micropolitan Statistical Area.
According to the U. S. Census Bureau, the county has a total area of 578 square miles (1,500 km2), of which 573 square miles (1,480 km2) is land and 5.0 square miles (13 km2) (0.9%) is water.