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Measuring 83 feet long, 37 feet wide and 23 feet high, Madison Boulder, a rectangular granite boulder is the largest known glacial erratic in North America. It illustrates the power of an ice sheet to move large blocks of fractured bedrock over substantial distances.
Location: Carroll County, NH
Year designated: 1970
Please remember, National Natural Landmarks (NNLs) are not national parks. NNL status does not indicate public ownership, and many sites are not open for visitation.
Last Updated: June 28, 2012