This spring, for the first time in more than two centuries, American shad, striped bass, and river herring may spawn in White Clay Creek, a tributary of the Delaware River in northern Delaware. Early one morning last month, a five-person crew waded into the frigid creek and pulled down most of a timber-and-stone dam that had blocked the river's flow since the early years of the Revolutionary War.

The White Clay Creek dam was the first ever removed in the state of Delaware, but it was far from the only one removed in the United States last year. On Tuesday, the conservation group American Rivers announced that 72 dams were torn down or blown up in 2014, restoring some 730