Where is the world's largest Beaver dam?
We have heard the stories that the largest is somewhere in Three Forks, MT, but the best data I can find is that the largest is in Wood Buffalo Park in northern Alberta.
It is 2790 feet, or about a half mile in length. It makes sense that the longest dams would need to be built on gently-sloping, slow-moving wetlands in order to impound a good volume of water, while most Beaver-sized streams can be effectively dammed with shorter lengths, or a series of shorter lengths, as in the photo below (from this excellent Beaver photo site):