The Blackstone River is a river in the U.S. states of Massachusetts and Rhode Island. It flows approximately 48 mi (80 km) and drains a watershed of approximately 540 sq. mi (1,400 km²). Its long history of industrial use has left a legacy of pollution, and was characterized by the United States Environmental Protection Agency in 1990 as "the most polluted river in the country with respect to toxic sediments."