Extending twenty miles from Chappaqua to Yonkers, the Saw Mill River is a major natural resource in Westchester and a critical riparian corridor. It is the County’s southernmost tributary to the Hudson River and provides some of the only remaining habitat in this part of the County for a wide range of plants and animals. The swath of green land around the river is one of the few extended open space corridors below interstate 287, and it is used by thousands of bikers, joggers, rollerbladers, and fishermen. Yet, years of heavy land use, miles and miles of roadways, and high population density present serious challenges to the river, including flooding, pollution, streambank erosion, habitat loss, and ecosystem degradation. The Saw Mill River is also one of the major pollutants of the Hudson River.