Cromwell’s Falls
A brief history and description of the canal.

Locks And Canals Of The Merrimack River - Part I
Includes a brief history and description.

Locks And Canals Of The Merrimack River – Part II
A more extensive history and description.   Current photos.

The Incredible Ditch: A Bicentennial History of the Middlesex Canal
A brief history and description begins on page 48.