Madison Boulder Natural Area

🏆🏆🏆🏆🏆 World’s Largest Glacial Erratic — A 5,000-ton, 83-foot-long boulder — the LARGEST known glacial erratic in the world!

Madison Boulder Natural Area protects the Madison Boulder — at 83 feet long, 37 feet wide, and 23 feet high, weighing an estimated 5,000 tons, it is the largest known glacial erratic in North America and possibly the world! The boulder was plucked from a ledge 2 miles northwest by the Laurentide Ice Sheet during the last Ice Age (about 12,000 years ago) and carried here as the glacier melted. The boulder is a single piece of Conway granite — moved 2 miles by a mile-thick river of ice. It was designated a National Natural Landmark in 1970.

Visitor Information

Frequently Asked Questions

How did the glacier move a 5,000-ton boulder?

The Laurentide Ice Sheet was up to a mile thick and moved with incredible force. It plucked the Madison Boulder from a granite ledge 2 miles away and carried it like a pebble. When the glacier melted about 12,000 years ago, the boulder was gently deposited in its current location — perfectly balanced on the ground.

About Madison Boulder

Madison Boulder Natural Area in Madison protects one of the largest glacial erratics in the world — a boulder 83 feet long, 23 feet wide, and 37 feet high, weighing an estimated 4,662 tons. This massive chunk of granite was carried from a mountain ledge 4 miles to the northwest by glacial ice during the last Ice Age and deposited when the mile-thick ice sheet melted roughly 12,000 years ago. It is a National Natural Landmark.

Things to Do

Viewing one of the world’s largest glacial erratics (4,662 tons!), picnicking, photography, and contemplating the unimaginable power of mile-thick ice sheets that could move house-sized boulders like pebbles.

Wildlife & Nature

Madison Boulder Natural Area — in Madison — preserves the largest glacial erratic in New England and one of the largest in the world. The Madison Boulder — 83 feet long, 23 feet wide, and 37 feet high, weighing an estimated 5,000 tons — was transported by the Laurentide Ice Sheet from a ledge several miles north during the last ice age (approximately 12,000 years ago). The boulder is a National Natural Landmark. Chipmunks and red squirrels scurry around the base.

Nearby Attractions

Madison — adjacent — is a small White Mountains region town. Conway — 10 miles north — has the Conway Scenic Railroad and outlet shopping. Silver Lake — in Madison — has swimming. Mount Chocorua — 5 miles northwest — is one of the most photographed mountains in New Hampshire.