 By 1859, Isabella had sufficient settlement and interest in self-government that the State legislature authorized its organization.The county name recognized Queen Isabella I of Castile, who with her husband Ferdinand commissioned Columbus's expedition in which he discovered the New World, based on a suggestion by Henry Rowe Schoolcraft, the US Indian Agent in this area in the late 19th century and an ethnologist.Isabella County comprises the Mount Pleasant, MI Micropolitan Statistical Area in Mid-Michigan, also known as Central Michigan.