Driftless Area, North America

Area: 12-15,000 sq. mi. (31,080-38,850 sq. km)
States included: 4
Warm as it may seem to concerned citizens around the globe, talk to a geographer or a geologist and they’ll tell you we’re actually in the middle of an ice age (albeit a milder period known as an interglacial). The last interglacial, which ended about 120,000 years ago, was followed by the advance of ice sheets in North America as far south as New York City and St. Louis, Missouri. The deep valley now occupied by Lake Michigan as well as the erosion-resistant rock in northern Wisconsin protected a swath of land called the Driftless Area from sheets of ice that altered much of the terrain in the Upper Midwest. The Driftless Area’s uniquely rugged topography also contains an abundance of caves and sinkholes.

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