The Middlesex Canal was a 27-mile (44-kilometer) barge canal connecting the Merrimack River with the port of Boston. When operational it was 30 feet (9.1 m) wide, and 3 feet (0.9 m) deep, with 20 locks, each 80 feet (24 m) long and between 10 and 11 feet (3.0 and 3.4 m) wide. It also had eight aqueducts.
Built from 1793 to 1803, the canal was one of the first civil engineering projects of its type in the United States, and was studied by engineers working on other major canal projects such as the Erie Canal. A number of innovations made the canal possible, including hydraulic cement, which was used to mortar its locks, and an ingenious floating towpath to span the Concord River. The canal operated until 1851, when more efficient means of transportation of bulk goods, largely railroads, meant it was no longer competitive.
In 1967, the canal was designated a National Historic Civil Engineering Landmark by the American Society of Civil Engineers. Remnants of the canal still survive and were the subject of a 1972 listing on the National Register of Historic Places, while the entire route, including parts that have been overbuilt, is the subject of a second listing in 2009.
History
Conception
By 1790, England had thirty years and all of continental Europe's many canals to draw on for the experience. In the years after the American Revolutionary War, the young United States began a period of economic expansion away from the coast. American men of influence had always kept an eye on news from Europe, especially from Great Britain, so when in the years from 1790–1794 the British Parliament passed eighty-one canal and navigation acts, American leaders were paying attention.
In Massachusetts, several ideas were proposed for bringing goods to the principal port, Boston, and connecting to the interior. For about three years there were plans to connect the upper reaches of the Connecticut River, above the falls at Enfield Connecticut, to Boston through a canal to the Charles. Sullivan was made the company's president; its vice president and eventually chief engineer was Loammi Baldwin, a native of Woburn, who had attended science lectures at Harvard College and was a friend of physicist Benjamin Thompson.