South of the reservoir, it flows through the Oradell Dam through River Edge, Hackensack, Teaneck, Bogota, and Ridgefield Park, once again approaching within 3 mi (5 km) of the Hudson, and separated from it by the ridge of the Palisades.

The name of the Hackensack River comes from the Lenape word Achinigeu-hach, or Ackingsah-sack, meaning "flat confluence of streams"[citation needed] or "stony ground".

At the outset of the colonial era, the river's watershed was home to Lenape groups now known as the Rumachenanck (or Haverstraw), Tappan, and Hackensack, the latter exonym taken from an encampment near the confluence of the tributary Overpeck Creek.

[3] European settlement began in the mid-17th century as part of New Netherland, when the region was called Achter Kol, meaning "rear pass" or "behind the ridge", to describe the valleys west of the Hudson Palisades, which afforded passage to trapping grounds in the northern hinterlands.

Human alterations to land in the Hackensack meadowlands increased in the 19th century, including clearing forests, building roads, railroads, and ditches, and filling wetlands.

The economic development and population increases in the watershed led to extensive water pollution in the river, both from municipal sewage and industrial wastewater.

The construction of the Oradell Reservoir dam in 1921 essentially changed the lower river from a free-flowing stream into a brackish estuary, allowing the encroachment of marine species.

[4]: 112  Urbanization in the region intensified after World War II, with the expansion of roads and highways, including the New Jersey Turnpike (1952),[6] as well as the Meadowlands Sports Complex (1970s).

[10][11][12] The river recovered somewhat by the late 2000s, following the decline in manufacturing in the area, as well as from enforcement of Clean Water Act regulations and from the efforts of local conservancy groups.