Falling water powered machinery by being diverted with dams into raceways, through water wheels, and back to a stream or river through a tailrace. Valley Falls was perhaps the best potential site for waterpowered mills on the Blackstone because the marsh upriver could become a storage pond and the relatively low banks along the tails provided mill sites. A sequence of three dams at Valley Falls and the raceways there illustrate this history of waterpower. Along the Blackstone River, which drops 438 feet in 46 miles, mill owners once used almost all of the river's energy. The first Wilkinson dam, built about 1813 on bedrock near the upper end of the falls, was replaced in 1828 by a dam 5 or 6 feet higher about 40 feet downstream, creating a larger pond in the Valley Falls marsh. The higher pond levels flooded waterwheels at mills upriver, and a lawsuit led to the dam crest being lowered 16 inches in 1835. A larger pond appears on an 1831 map, while an 1838 map made after the lowering shows a smaller pond, and later siltation behind the Valley Falls dam reduced the pond further. Gates in arches below controlled water flowing from the river into the raceways, and a gatehouse across the river sheltered the machinery. Archaeological investigations in February 1991 located the buried headrace from the 1813 and 1828 dams, and much of the timber framing from both Wilkinson dams still remains underwater, last exposed when water behind the stone dam was lowered in 1940.