What major river runs through Boston?

The Charles River (sometimes called the River Charles or simply the Charles) is an 80 mi (129 km) long river in eastern Massachusetts. From its source in Hopkinton the river flows in a northeasterly direction (after first coursing due south through Milford), traveling through 23 cities and towns before reaching the Atlantic Ocean at Boston.

Brandeis University, Harvard University, Boston University, and the Massachusetts Institute of Technology are located along the Charles River. Near its mouth, it forms the border between downtown Boston and Cambridge and Charlestown. The river opens into a broad basin and is lined by the parks of the Charles River Reservation. On the Charles River Esplanade stands the Hatch Shell, where concerts are given in summer evenings. The basin is especially known for its Independence Day celebration.

Captain John Smith explored and mapped the coast of New England, naming many features, originally naming the Charles River the Massachusetts River, which was derived from the tribe living in the region. 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.