The Watchung Mountains are a group of three long low ridges of volcanic origin, between 400 and 500 feet (120 and 150 m) high, lying parallel to each other in northern New Jersey in the United States.

The Watchung Mountains are known for their numerous scenic vistas overlooking the skylines of New York City and Newark, New Jersey, as well as their isolated ecosystems containing rare plants, endangered wildlife, rich minerals, and globally imperiled trap rock glade communities.

Parks, preserves, and numerous historical sites dot the valleys and slopes of the mountains, providing recreational and cultural activities to one of the most densely populated regions of the nation.

[9][10] Evidence of the Lenape presence in the Watchungs can be seen in numerous camps sites that have been uncovered, mainly along the rivers coursing through mountains and in the small caves abundant in the volcanic rock.

It is thought that the Lenape favored the Watchungs for their profusion of natural resources, including abundant freshwater rivers and streams, a variety of forests, and plentiful fish and game.

Trade in furs to European markets, a bounty of game and fish, and native garden produce for the traders was important during the Dutch colonial period when few settlements occurred.

[5] Localized deformation of the western edge of the basin along the Ramapo Fault System formed alternating synclines and anticlines that warped the layers of basalt and sedimentary rock.

[5] It is in these synclines that the basalt layers are thick and warped into downward dipping trap rock sheets, descending below the current erosional surface of the basin.

Elsewhere in the Newark Basin, smaller synclines preserve the Watchung Outliers, additional fragments of the flood basalts and associated overlying sediments that have survived into the modern era.

[5] Because the majority of the Watchung Mountains are composed of extrusive igneous trap rock, they display characteristic columnar jointing and stacked lava flows.

[9] The magma that generated the Watchungs and the Palisades also formed the intrusive igneous Sourland Mountain in Central New Jersey, as well as a series of smaller outlying volcanic ridges in the region.

[citation needed] The Metacomet Mountains in the Connecticut River Basin, another aborted rift valley, came into existence at approximately the same time as the Watchungs, also through extrusive eruptions.

[citation needed] Due to the volcanic nature of the Watchungs, zeolites, including prehnite, analcime, and stilbite, which form from a reaction of mafic rocks in alkaline environments, can be found along exposed ridge lines.

[20] In the mid-twentieth century, the ability of the Watchungs to hold back the spread of urbanization was greatly reduced with the development of the interstate highway system.

[citation needed] Today, along the summits of the Watchungs, talus slope environs as well as globally rare trap rock glade/outcrop communities and their unique species have become threatened by development.

Retained within the embrace of Third Watchung Mountain, the Great Swamp National Wildlife Refuge consists of 7,600 acres (31 km2) or approximately 12 square miles (30.4 km²) of varied habitats.

The refuge was created through the efforts and donations of a small group of local residents in 1959, the Jersey Jetport Site Association, and a Great Swamp Committee later formed within the North American Wildlife Foundation.

[citation needed] General awareness of the history and natural environment of Watchungs has been increased through efforts such as the construction and designation of the Lenape Trail.