This is an image of a large rock formation off the coast of Michigan in Lake Huron. The formation is a single rock that has become separated into two large sections by erosion.

The L.L. Cook Co., Milwaukee, WI

The description states:

183-S MICHIGAN THUMB SCENERY

Sister Rocks — off Broken Rocks, Port Austin, Michigan

–The Broken Rocks area of the lake refers to the off-shore formations of rock that have become separated from the shore and are now free-standing in the lake.

This postcard is dated 1957.