Just how durable are beaver dams? A map from 1868 showing beaver dams across a portion of Michigan still exist 150 years later.

The map is from an 1868 publication The American Beaver and His Works (actually available on Amazon), studying beaver habitat around the Ishpeming area in Michigan's Upper Peninsula and shared by AtlasObscura.

The 1868 book that first identified these beaver dams was written by Lewis Henry Morgan, a railroad executive and scholar interested in the relationship both people and animals have with each other.

When modern-day ecologist

Carol Johnston first saw Morgan’s map, she realized she had a unique opportunity to see how the Ishpeming area’s beavers fared as the railroad opened up their territory to human development. Johnston compared Morgan’s map to one she made herself last year using recent aerial photographs, and found evidence that some 75 percent of the dams and ponds that Morgan documented were still discernible.

The Long Life of Michigan Beaver Dams

That seems simply remarkable. Natural objects built around the time of America's Civil War are still in existence today. Rebuilt, no dobut, by these animals as the wood would naturally decay.

Science reports that beavers can occupy a colony for 1000 years, so call this spot in Michigan's Upper Peninsula the Beaver Millenium. These dams observed by a railroad baron in the 1860s was found to still be in existance in the 2000s and will likely be here for hundreds more years.

See the full map and read more at AtlasObscura. You'll be able to pick out the Imspeniming area and the natural features of the area.

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