Marlette, MI: A Complete Guide to Michigan’s Hidden Gem in the Heart of the Thumb Marlette, Michigan, often referred to as the “Heart of the Thumb,” is a small yet vibrant city located in Sanilac County. This quaint Midwestern town combines rural charm with a rich history, strong community values, and an inviting atmosphere. From… Exploring Marlette, MI: The Heart of Michigan’s Thumb – Travel