American Rivers provides this cool interactive map of all dams removed in the US since 1936. It does have a few little quirks, including locating an Illinois dam a bit too far west on the Clearwater River in Idaho. But it is cool to see how many dams have been removed. I had forgotten that an old dam was recently removed near my home in Moscow. I ride my bike past the location regularly and watched it happen, but it now looks so natural that the memory of the dam has faded.
