 For the last few miles it forms the boundary between the Towns of Brownville and Hounsfield.There are at least 17 dams on the Black River, with eight in the upper part above Lyons Falls, and nine below Watertown.The upper and lower reaches of the river have a steep gradient and were originally developed to provide mechanical power for mills, such as the old Georgia-Pacific paper mill (which now sits abandoned and falling into disrepair) in Lyons Falls, and later hydroelectricity.