Everything about the Mill River starts here. The river takes its name from the mills built on its banks to use the current, and the first of them — Christopher Todd's gristmill, grinding corn for the colony — stood on this spot from 1642. By 1780 there were eight mills on the river. Farmers rented time at them to grind their grain.
1798
In 1798 Eli Whitney bought Todd's mill and the ground around it, and built an armory.
Whitney is remembered for the cotton gin, which he patented in 1794 and made almost nothing from, because it was too easy to copy. The armory was the second act. He took a contract to supply muskets to the United States Army — a large order, on a short deadline, with no workforce of trained gunsmiths to draw on.
His answer was to change what a worker had to be able to do. Instead of one craftsman filing a whole gun to fit itself, machines guided by jigs and patterns would cut each part close enough to a standard that any part would fit any gun. The skill moved out of the hand and into the machine.
Whitney did not invent the idea, and historians have spent a long time arguing about how completely his own muskets achieved it. But the method that came out of this riverbank — interchangeable parts, machine tools, division of labour — is the one that made American mass production possible. The water turned the machinery.
The fires
By the middle of the 19th century New Haven had a serious fire problem. The population was growing, houses stood close together, and light and heat came from oil lamps and open flames. Fires started often and ran through whole blocks.
The water to fight them came from the Mill River and from the Farmington Canal. When the canal was drained and converted into a railway, that second source disappeared, and the city was left short.
Eli Whitney Jr. — the inventor's son, running the family works upstream in Whitneyville — led the effort to found the New Haven Water Company and to dam the river properly. He had his own reason as well: a higher dam meant more head, and more head meant more power for his mills.
The dam
The original dam was wooden. Whitney and his son rebuilt it in masonry and raised it repeatedly: from roughly six feet to about twenty-seven in 1860, to thirty-one in 1866, and by another nineteen inches in 1916, which is close to its height today.
The reservoir it created was named Lake Whitney, and for about a hundred and thirty years it was a major part of the public water supply for New Haven County. It served in that role until 1991. The upper Mill River is still strictly regulated because of it — industry was removed from the river above the reservoir, and the water quality upstream has stayed good.
What a dam costs
A dam is a wall across a migration route. River herring — alewives and blueback herring — spend their lives at sea and return to fresh water each spring to spawn, and before 1860 they could run the length of the Mill River. After 1860 they could run as far as this wall.
That is the trade the city made, and it is one the region has been slowly revisiting: fish passage, fishways and dam removals across Connecticut have been reopening rivers to the spring run.
The site today
The armory site is now the Eli Whitney Museum, and the barn, the dam and the water works are the most legible industrial landscape on the river. Downstream from here the Mill River becomes something else entirely — tidal, filled, bridged, and built over — but this is where it began.