These low falls and rapids on the Merrimack River were altered by the dam here that diverts water at the top of the falls into the canal raceways running downstream through the town of Lowell. The first dam at the falls was built in 1820, and Lowell grew to be one of the earliest and largest planned factory cities in the USA. Its dozens of red brick mill buildings are an impressive sight, and recur in other New England mill cities like Lawrence, Manchester, Chicopee, and Holyoke. These falls were named after the small falls in Pawtucket, Rhode Island, where America’s industrial revolution is said to have begun, in 1793, with the construction of the Slater Mill.