[5] With the construction of the Kensico Dam in 1885, however, the river was cut off from its natural headwaters and today a small tributary stream originating from the reservoir serves as its source.

The Bronx River flows south past White Plains, then south-southwest through the northern suburbs in New York, passing through Edgemont, Tuckahoe, Eastchester, and Bronxville.

At Bronxville, it is fed by Sprain Brook, its longest tributary system, which originates at Greenburgh Town Park.

It empties into the East River, a tidal strait connected to Long Island Sound, between the Soundview and Hunts Point neighborhoods.

[9] The acca- element, as represented in the Long Island place-name Accabonac, was deformed into the more familiar, suitably watery European morpheme aque-.

In December 1948, flow of the Bronx River was changed to eliminate a curve in its course in Bronxville, to create land on the old riverbed on which to construct an addition to Lawrence Hospital.

[12] The river became a favorite project of U.S. Representative José Serrano, who secured US$14.6 million in federal funding to support the rehabilitation of the waterway, into which some Westchester towns continued to discharge raw sewage intermittently, as sanitary sewer overflows, as late as 2006.

Under a November 2006, agreement, the municipalities of Scarsdale, White Plains, Mount Vernon and Greenburgh agreed to stop dumping sewage in the Bronx River by May 2007.

Their offspring spend the summer in the river, migrate out to sea in the fall, and in three to five years return, like all anadromous fish, to their spawning grounds.

[18] In February 2007 biologists with the Wildlife Conservation Society, which operates the Zoo, spotted a beaver (Castor canadensis) in the river.

It sounds fantastic, but one of the messages that comes out of this is if you give wildlife a chance it will come back," said John Calvelli, a spokesman for the Society.

[19][20][21] The beaver is named Jose Serrano, after the Congressman, and was sighted below the East Tremont bridge at Drew Gardens as recently as June 2009.

[33] According to the NYC Department of Environmental Protection: "At the beginning of the 18th Century, roughly 12 water mills were producing paper, pottery, flour, tapestries, and snuff along the Bronx River.