High Quality Content by WIKIPEDIA articles! The Thumb is a region and a peninsula of Michigan, so named because the Lower Peninsula is shaped like a mitten; thus the Thumb is the area that looks like the thumb of the mitten. The Thumb is generally considered to be in the Mid-Michigan area of the state, located east of Flint/Tri-Cities region, and north of Southeast Michigan. The thumb is also branded as the Blue Water Area of Michigan.