A Different New Jersey

Approximately 25,000 years ago, the Laurentide Ice Sheet reached its maximum extent in this region. It covered northern New Jersey beneath hundreds or possibly thousands of feet of ice. Its southern edge crossed the state from near the Delaware Water Gap through northern Morris County and continued across what are now Staten Island and Long Island. As the glacier advanced, it scraped and reshaped the land, moved enormous quantities of rock and soil, and created the terminal moraine that still marks its southernmost reach.

As the climate warmed, the ice began retreating northward. It left behind ridges of stone, broad valleys, wetlands, and enormous lakes formed when ice and glacial debris blocked existing waterways. One was Glacial Lake Passaic, which covered much of the lowland west of the Watchung Mountains. As the lake eventually drained, portions of its former lakebed remained waterlogged. Today’s Great Swamp is one of the most visible remnants of that ancient glacial lake.

By 15,000 years ago, the glacier had disappeared from New Jersey, although the climate remained considerably colder than it is today. Spruce, pine, open grassland, and patches of tundra covered a landscape that would have looked more like southern Canada than modern New Jersey. Powerful rivers carried meltwater, sand, gravel, and glacial debris southward toward a coastline far beyond the present Jersey Shore.

New Jersey was also much larger. Sea level was approximately 300 feet lower because enormous quantities of water remained locked in the world’s ice sheets. The Atlantic coastline lay about 100 miles east of the present Jersey Shore. The Hudson and Delaware rivers continued across an immense coastal plain that is now submerged beneath the ocean, and Long Island formed part of this broader Ice Age landscape.

By around 15,000 years ago, some of the earliest Paleoindians may have entered or traveled through this changing landscape. They followed rivers and animal herds, gathered wild plants, and carried carefully crafted stone tools. Some may have lived or camped on the vast coastal plain that now lies beneath the Atlantic Ocean. As the glaciers continued melting and the sea rose, that land gradually disappeared beneath the water, taking much of its archaeological record with it. What is now the ocean floor was once a living landscape of rivers, forests, wetlands, animals, and perhaps some of New Jersey’s earliest people.

Mastodons wandered through New Jersey’s forests and swampy wetlands, feeding on branches, leaves, and aquatic vegetation. Their remains have frequently been preserved in former bogs, swamps, and lake beds. Caribou, elk, and other cold-adapted animals also moved through the region. Although Paleoindians and mastodons likely occupied New Jersey during overlapping periods, no known archaeological site in the state provides direct evidence that Paleoindians hunted or killed mastodons.

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