Mapping the Historic Mill River
In the 1640s, when English colonists first contacted the local Nonotuck Indians, the Mill River's mouth was located in Hulbert's Pond, leading into Easthampton's Manhan River. After settling Northampton in the middle of the 17th century, colonists converted the native meadow vegetation to fodder for their livestock. However, the Mill River often flooded the Manhan Meadows at inconvenient times (see map, so the colonists tried to dike it.
When the dikes did not work the settlers dug a ditch in about 1720, diverting the Mill River directly through the meadows, into the Connecticut River.
Over the course of the 19th century, Northampton expanded into the flood plain, so both the Connecticut and Mill Rivers would often flood adjacent areas. After the disastrous storm of 1936, Northampton asked the Corps of Engineers in 1940 to divert the river from the center of downtown Northampton into Hulbert's Pond, the river's original mouth.
Here is a terrain map of Nonotuck/Northampton ca. 1660.
Here is a map of the Mill River Diversions: