Where are erratics in the great lakes region?

Answer 1

Erratics are boulders transported and deposited by a glacier. Their composition (lithology) is different than the bedrock upon which they are sitting.
The Great Lakes region was once covered by glaciers. Photos of glacial erratics in Wisconsin at second url.
Photo and location of erratic in New York, third url.
Photo and discussion of erratics in Minnesota, fourth url.

Answer 2

it is said in the great book that they are all hidden under like michigan...