It is centered on the North Canal and the Great Stone Dam, which provided the waterpower for its many mill complexes.

In 1845 they company acquired land from then towns of Methuen and Andover and began construction on the North Canal and the Great Stone Dam.

[2] The Great Stone Dam was constructed across the Merrimack River at a place called Bodwell's Falls, where there is a five-foot drop.

[2] The Pacific Mills complex is an extensive array of buildings in the western (upper) and central parts of the district.

In the central part of the district the Pacific Mills include buildings in which both cotton and worsted wool products were manufactured.

Other notable buildings here include the Essex Company Offices and Yard (separately listed on the National Register).