Charles River, MA

The longest river wholly within the state, the Charles River is slightly more than 80 miles long, following a winding course (south, northeast, north, east, northwest, and east) from its source in Hopkinton, southern Middlesex County, to its mouth on Boston Harbor, dividing Cambridge and Boston.  The river travels through 22 cities and towns until reaching the Atlantic Ocean.

Despite the river's length and relatively large drainage area (308 square miles; 798 km²), its source is only 26 miles (42 km) from its mouth, and the river drops only 350 feet (107 m) from source to sea.  The river is dammed near its mouth, but navigation locks provide harbor access. In the mid-19th century much of the marshy area at the river’s mouth, known as the Back Bay, was filled in. Charlesbank Park in Boston, on a portion of that land, provides footpaths, playgrounds, ponds, and a music shell for summer concerts. Canoeing is a popular sport, and college crews sail and row along the river. The Head of the Charles regatta is a two-day rowing event that has been held each autumn since 1965. Until the mid-20th century the Charles was popular among swimmers and fishers, but, despite extensive pollution-control measures enacted from the 1970s, the water quality remained substandard in the late 1990s.

Within its drainage basin of 307 square miles (795 square km) are more than 30 square miles (78 square km) of wetlands, supporting such rare plants as the great laurel rhododendron, dragon’s-mouth, and river bulrush. Rare animals include the mud puppy (blue-spotted salamander) and the spotted turtle.