Lowell's Canal System
The Lowell Canal system evolved steadily from 1821, when the Boston Associates purchased the old Pawtucket transportation canal in East Chelmsford (which later became Lowell). They initially used the Pawtucket as a feeder canal to channel water into new power canals. Just above Swamp Locks, the Merrimack, Western, and Hamilton canals branched off, taking water to the Merrimack, Lowell, Tremont, Suffolk, Lawrence, Hamilton, and Appleton mills. Only the Merrimack Company used the full 30-foot drop of water; for other mills the drop was 13 or 17 feet.
In 1847 the construction of the Northern Canal increased waterpower generation by the canal system by 50 percent. By mid-century the canal system we see in Lowell today was in place. Including almost 6 miles of canals and operating on two levels, this system powered 10 major mill complexes employing more than 10,000 workers.
Source: Lowell National Historical Park Handbook 140