The Charles River is a small, relatively short river in Massachusetts, USA, that separates Boston from Cambridge and Charlestown. It is fed by about 80 brooks and streams and several major aquifers as it flows snakelike for 80 miles (129 km), starting at Echo Lake in Hopkinton, through 22 cities and towns in eastern Massachusetts before emptying into Boston Harbor. Its watershed contains 33 lakes and ponds, and 35 communities are entirely or partially part of the Charles River watershed. 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. It is the most densely populated river basin in New England.
Brandeis University, Harvard University, Boston University, and the Massachusetts Institute of Technology are all located along the Charles River; at Boston proper it opens out into a broad basin and is lined by parks such as the Charles River Esplanade (in which stands the Hatch Shell, where concerts are given in summer evenings) especially known for its Independence Day celebration. The river is well known for its rowing, sculling, and sailing, both recreational and competitive. The Head of the Charles Regatta is held annually, in October.
Captain John Smith explored and mapped the coast of New England, naming many features including the Charles River, which he gave the Native American name, Massachusetts River. When Smith presented his map to Charles I he suggested that the king should feel free to change any of the "barbarous names" for "English" ones. The king made many such changes, but only four survive today, one of which is the Charles River, which Charles named for himself.
Subsequent European settlers harnessed the river for industrialization, and by 1640 entrepreneurs on the Neponset River had diverted its water to power their mills.
Waltham was the site of the first fully integrated textile factory in America, built by Francis Cabot Lowell in 1814, and by the 19th century, the Charles River was one of the most industrialized areas in the United States. Its hydropower soon fueled many mills and factories. By the century's end, 20 dams had been built across the river, mostly to generate power for industry. An 1875 government report listed 43 mills along the 9.5-mile (15 km) tidal estuary from Watertown Dam to Boston Harbor.
In portions of its length, the Charles drops slowly in elevation and has relatively little current. Despite this, early settlers in Dedham, Massachusetts, found a way to use the Charles to power mills. In 1639, the town dug a canal from the Charles to a nearby brook that drained to the Neponset River. By this action, a portion of the Charles's flow was diverted, providing enough current for several mills. The new canal and the brook together are now called Mother Brook. The canal is regarded as the first industrial canal in North America. Today it remains in use for flood control.
Today's Charles River basin between Boston and Cambridge is almost entirely a work of human design. Its design was the work of noted landscape architects Charles Eliot and Arthur Shurcliff, both of whom had apprenticed with Frederick Law Olmsted, and by the architect and landscape architect Guy Lowell. This designed landscape now includes over 20 parks and natural areas along 19 miles (31 km) of shoreline, from the New Dam at the Charlestown Bridge to the dam near Watertown Square.
Eliot first envisioned today's river design in the 1890s, but major construction began only after his death with the damming of the river's mouth at today's Museum of Science, an effort led in by James Jackson Storrow. The new dam, completed in 1910, stabilized the water level from Boston to Watertown, eliminating the existing mud flats, and a narrow embankment was built between Leverett Circle and Charlesgate. After Storrow's death, his widow Mrs. James Jackson Storrow donated $1 million toward the creation of a more generously landscaped park along the Esplanade; it was dedicated in 1936 as the Storrow Memorial Embankment. This also enabled the construction of many public docks in the Charles River Basin. In the 1950s a highway (Storrow Drive) was built along the edge of the Esplanade to connect Charles Circle with Soldiers Field Road, and the Esplanade was enlarged on the water side of the new highway.
Once popular with swimmers, awareness of the river's high pollution levels forced the state to shut down several popular swimming areas, including the Cambridge's Magazine Beach and Gerry Landing public beaches. Until very recently, rowers and sailors who fell into the water were advised to go to the hospital for tetanus shots.
Efforts to clean up the river and restore it to a state where swimming and fishing would be acceptable began as early as the 1960s and the program to clean up the Charles for good took shape in 1965 with the creation of the Charles River Watershed Association. In 1995, the United States Environmental Protection Agency declared a goal of making the river swimmable by 2005. In 1996, then governor William Weld plunged, fully clothed, into the river to prove his commitment to cleaning up the river.
A combination of public and private initiatives helped dramatically lower levels of pollutants by focusing on eliminating combined sewage outflow and storm water runoff. A new Charles River Dam was constructed downstream from the Science Museum site to keep salt water out of the basin. Since Weld's stunt, the river's condition has improved dramatically, although it was not deemed entirely swimmable by 2005. In 1995 the EPA rated the river's quality as a "D" compared to the most recent ranking of a "B+" and most days of the year, the river now meets swimming standards below the Massachusetts Avenue bridge. With the improved water quality, swimming and fishing are progressively re-emerging as about 90% of the length of the river is now considered safe for swimming. Health risks remain, however, particularly after rainstorms and when walking in certain riverbeds stirs up toxic sediment.
During the period September 2004 to September 2006, the City of Cambridge and the state's Department of Conservation and Recreation introduced vegetation at Magazine Beach just west of the BU Bridge on the Cambridge side of the river. This introduced vegetation had significant trouble living there because it was not native to the Charles River. The vegetation installed created a wall preventing the reintroduction of swimming at Magazine Beach.
It is a common belief that the water quality of the Charles River is at its worst after a large rainfall because of pollutants carried by runoff. However, a study, published in the Journal of the American Water Resources Association (April 2008), completed by researchers at Northeastern University, found high concentrations of E. coli bacteria in the Charles River after a long period of no rain. Using a mathematical model, the researchers then determined that two major tributaries, the Stony Brook and Muddy River, are the predominant sources of E. coli in the lower Charles River.