Geography of the Blackstone Valley

Blackstone River meandering through valley with fall foliage.
Photograph from Lookout Rock of the Blackstone River, Uxbridge, Massachusetts

The Blackstone River is about 15,000 years old. A massive glacier once covered New England carving a deep, U-shaped valley as it moved south like a giant snowplow. When the glacier receded, it left behind a river valley with a steady drop. It also provided many sites that were ideal for the construction of dams. The dams created barriers that slowed down or stopped the movement of water.

The average dam in the Blackstone Valley was only about nine feet tall. Even small dams were important for mill owners. Building a dam causes the water in the river to rise until it flows over the dam as a waterfall. The rising water created reservoirs or mill ponds that allowed mills to operate their water wheels almost all year long They provided a steady source of water even in times of drought.

 
Dam with rolling water over the top of it. Whitin Machine Work factory building in the background
Whitinsville Dam with Whitin Machine Work in background, Whitinsville, Massachusetts
The Blackstone River drops about 440 feet over its 46-mile length. That’s an average drop of about 9 ½ feet per mile. This drop is important. Water weighs 8.34 pounds per gallon. It is the weight, not the speed of the water that pushed the water wheels that powered the mills. The series of drops along the Blackstone over multiple rapids and waterfalls, made it perfect for the construction of water-powered mills.

The geography and geology of the Valley made this relatively small and seemingly ordinary New England River the birthplace of the American Industrial Revolution. Eventually it won the nickname of “America’s Hardest Working River.”
 

Last updated: July 25, 2021

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