There is evidence indicating the Delaware River likely supported at least one such Lenape settlement at the southern foot of the mountain around present-day Lambertville, New Jersey.

Goat Hill comprises the highest point of the main ridge before reaching the southernmost end of Sourland Mountain at the Delaware River.

[6] West of the main ridge, near Flemington, is Prospect Hill, a volcanic remnant lying along the western edge of the Amwell Valley.

[7] Sourland Mountain was formed 200 million years ago by a plutonic intrusion of a hard igneous rock, diabase, into the Brunswick Shale.

However, the diabase and related hornfels which form the backbone of the mountain are a type of highly erosion resistant stone known as trap rock.

Consequently, millions of years of erosion lowered the more easily worked shale surrounding the intrusion, turning it into the elevated ridges which currently comprise Sourland Mountain.

The Palisades Sill, in northeastern New Jersey and southeastern New York, was not only formed under similar circumstances to Sourland Mountain, it is at least partly contiguous with it.

One such dike extending northwest from Sourland Mountain has been determined to be responsible for the creation of Prospect Hill, an extrusive basalt peak near Flemington, New Jersey.

[12] Sourland Mountain is in the Northeastern coastal forests ecoregion[13] It is an environmentally sensitive area and is home to several rare and threatened plants and animals, including: trout lilies, wood anemones, ginseng, spotted salamander, pileated woodpecker, bobcat, wood turtle, barred owl, bobolink, Cooper's hawk, grasshopper sparrow, Savannah sparrow, upland sandpiper, and the scarlet tanager.

Being the largest contiguous forest between the Pine Barrens and the New Jersey Highlands, it is critical to the survival of neotropical migrant birds and other rare species of plants and animals.

D&R Greenway Land Trust's partner in Mexico, Amigos de Calakmul, protects bird habitat at the southern end of the migratory flyway.

Notable residents of the Mountain include: playwrights Eugene O'Neill, aviator Charles Lindbergh, patriot John Hart (signer of the Declaration of Independence), the painter George Bellows, and freed slave and tavern owner Sylvia Dubois.