Here is a great shot of North Charleroi, Pa., taken from the air before the dam, at right, along the Monongahela River was relocated in the 1930s.
Some 80 years later, the replacement locks and dam is undergoing renovations to keep navigation moving at a quicker pace on the Mon.
Click here to see the top photo in a larger format.
Ditto here to see the other one huge.
(The old photo is courtesy of the Charleroi Area Historical Society while the new one is property of the Observer-Reporter newspaper in Washington, Pa.)