Saco, river, c.105 mi (170 km) long, rising in the White Mts., N central N.H. and flowing SE through Maine to the Atlantic Ocean below Biddeford. The falls at Biddeford, site of a hydroelectric dam (opened 1949), were an early source of water power for the textile industry there, which has declined significantly.
Saco (sô`kō), city (1990 pop. 15,181), York co., SW Maine, on the Saco River; settled 1631, inc. as Pepperellboro 1762; name changed to Saco 1805; inc. as a city 1867. Saco is named for the Sawatucke ethnic group and means "burnt pine." The city has an industrial park and makes diverse products, such as machinery, leather, and shoes. Thornton Academy is located there.