Connecticut River

The Connecticut River is the largest and longest river in New England, and also an American Heritage River. It flows roughly south, starting from the Fourth Connecticut Lake in New Hampshire. After flowing through the remaining Connecticut Lakes and Lake Francis and leaving the town of Pittsburg, it defines the border between the states of New Hampshire and Vermont. The river then flows through the fertile Pioneer Valley of western Massachusetts and past Springfield, the most populous city on the river. 4 miles (6 km) south of Springfield, the river enters Connecticut, where it spurred the growth of Hartford, the second largest city (and only state capital) along the river, situated just 24 miles (39 km) miles south of Springfield. From Hartford, the Connecticut River veers southeastward and ultimately discharges into the Long Island Sound at Old Saybrook and Old Lyme, Connecticut. The Connecticut River has a total length of 407 miles (655 km), and a drainage basin extending over 11,250 square miles (29,100 km2). The mean freshwater discharge into Long Island Sound is 19,600 cubic feet (560 m3) per second.

The Connecticut River is tidal up to Windsor Locks, Connecticut, approximately 60 miles (100 km) from the mouth. Major tributaries include the Ashuelot, West, Miller's, Deerfield, White, Westfield, Farmington, and Chicopee rivers. The Swift River, a tributary of the Chicopee, has been dammed and largely replaced by the Quabbin Reservoir which provides water to the Massachusetts Water Resources Authority district in eastern Massachusetts.

The river carries a heavy amount of silt, especially during the spring snow melt, from as far north as Quebec. The heavy silt concentration of the river forms a large sandbar near its mouth on Long Island Sound and has historically provided a formidable obstacle to navigation. The difficulty of navigation on the river is the primary reason that it is one of the few important rivers in the United States without a major city at its mouth. The Connecticut River estuary and tidal wetlands complex is listed as one of the 1,759 wetlands of international importance under the Ramsar Convention on Wetlands.