Which Great Lake has the largest freshwater dune system in the world?

Lake Michigan has the largest freshwater dune system in the world.

Its eastern shoreline contains extensive sand dunes created by waves, currents, wind, and fluctuating lake levels. The best-known areas include Sleeping Bear Dunes National Lakeshore in Michigan and Indiana Dunes National Park in Indiana. These landscapes are among the most prominent examples of freshwater coastal dunes anywhere.

Sleeping Bear Dunes National Lakeshore protects towering dunes, beaches, forests, and bluffs along the northeastern shore of Lake Michigan. Indiana Dunes, farther south, preserves a compact but exceptionally diverse shoreline environment beside the heavily developed southern end of the lake.

The dunes are sometimes mistaken for ocean coastlines because of their scale. They formed beside freshwater, not saltwater, and support specialized plants and habitats. Wind continues to move sand inland, while storms and changing lake levels reshape the shoreline.