Round Valley State Park
Clinton Township, Hunterdon County, NJ


Located one-half mile south of Lebanon, NJ. The area is accessed from US 22, 8 miles east of Clinton and 4 miles from Whitehouse. US 22 can be reached either from I-78 using exit 20A from the north or from I-287 from the east. Half a mile west of Lebanon, there is a sign to the park. Turn onto the park access road and travel for 2 miles. The park access road merges with County Road 629 later. Pass the road to the boat launch and, after approximately 1 mile, turn left into the Round Valley entrance.

Stop at the visitors center to get a car parking permit. Parking is not allowed at the center.

It is in a natural, horseshoe-shaped basin surrounded on three sides by Cushetunk Mountain. The reservoir covers more than 2,300 acres. Round Valley Reservoir is one of the largest and deepest lakes in NJ. Accessed from US 22, 8 miles east of Clinton and 4 miles from Whitehouse.

lots of fishermen

Superb view of rural NJ ahead.

large, open area

Red squirrels and the eastern chipmunk inhabit the dense woodland at Round Valley.

Audubon guide:

The recreation area is a horseshoe-shaped ridge encircling a reservoir.


The trap rock is a diabase (similar to that of the Palisades).

The rocks of this curving ridge had their origin in an intrusion of diabase between strata of the Brunswick shales and sandstones of the Triassic formation. They were eventually exposed by erosion, which wore down the softer shales above and around and left the harder igneous material standing 800 feet above sea level and 400 feet above the surrounding Hunterdon countryside.


A hiking trail almost 10 miles in length completely encircling the reservoir.

At the northern end of the horseshoe, descend in a northwesterly direction to Cherry Street to travel back to the cars, using the reservoir area instead of walking the road.

The Cushetunk Ridge, never having been glaciated as were the Palisades, has more residual soil than the latter. A good second growth of hardwood covers most of its upper portion.

The region is particularly attractive in spring, at the time of the blossoming dogwood, which is plentiful on the slopes of the ridge. There are good views eastward over the plain of the valley of the Raritan, bordered on the south by similar trap ridges, which are also southwestward extension of the Palisades intrusion.

Ask for a free trail map when you sign in at the visitor center.

A few minutes after starting out you'll come to a marvelous view of the narrow reservoir, one mile wide and three miles long. Eventually, after traversing open fields, the trail lead to thick woods before heading up a hill following the ridge line toward Cushetunk Mountain, a scenic spot to have lunch or a snack.


Half a mile west of the south limb of the Cushetunk horseshoe, in abandoned limestone quarries, are the remains of the kilns where the rock was burned. The rock has a peculiar blue color, possibly due to its manganese content.

Four miles north of Round Valley Reservoir a smaller horseshoe of diabase shows a curious topography. The Brunswick shales of the interior valley are open, while the contact with the trap rock and border conglomerates is generally indicated by the forest which covers the ridge.

In 1958 a natural horse-shoe shaped valley in the rolling hills of Hunterdon County was damned, and today 55 billion gallons of water fill this area, known as Round Valley Reservoir. The lake is 70-feet-deep. It is the deepest in the state.

Many fisherman come here. Lots of boats. Hike along a portion of the nine-mile trail.


Dr. Patrick L. Cooney

Acer negundo (box elder)
Acer rubrum (red maple)
Betula lenta (black birch)
Betula populifolia( gray birch)
Fraxinus sp. (ash)
Juniperus virginiana (red cedar)
Liriodendron tulipifera (tulip tree)
Morus alba (white mulberry)
Pinus strobus (white pine)
Platanus occidentalis (American sycamore)
Populus deltoides (cottonwood)
Populus grandidentata (big toothed aspen)
Prunus serotina (black cherry)
Quercus alba (white oak)
Quercus prinus (chestnut oak)
Rhus typhina (staghorn sumac)
Salix discolor (pussy willow)
Salix sp. (willow)

Elaeagnus umbellata (autumn olive)
Lonicera sp. (honeysuckle)
Rosa multiflora (multiflora rose)
Rubus occidentalis (black raspberry)
Rubus phoenicolasius (wineberry)
Vaccinium angustifolium (early low blueberry)
Viburnum acerifolium (maple leaf viburnum)

Lonicera japonica (Japanese honeysuckle) 10/1/96
Parthenocissus quinquefolia (Virginia creeper)
Toxicodendron radicans (poison ivy)
Vitis sp. (grape)

Achillea millefolium (yarrow)
Agrimonia sp. (agrimony)
Alliaria petiolata (garlic mustard)
Ambrosia artemisiifolia (common ragweed)
Artemisia vulgaris (common mugwort)
Asclepias syriaca (common milkweed)
Aster divaricatus (white wood aster) 10/1/96
Aster novae-angliae (New England aster) 10/1/96
Aster pilosus (heath aster) 10/1/96
Bidens cernua (nodding bur marigold) 10/1/96
Bidens connata (swamp beggar ticks) 10/1/96
Carya tomentosa (mockernut hickory)
Catalpa sp. (catalpa)
Centaurea nigra (black knapweed) 10/1/96
Cichorium intybus (chicory) 10/1/96
Cornus amomum (swamp dogwood)
Cornus florida (flowering dogwood)
Daucus carota (Queen Anne's lace) 10/1/96
Desmodium sp. (stick tight)
Epilobium sp. (willow herb)
Erechtites hieraciifolia pilewort)
Erigeron annuus (daisy fleabane) 10/1/96
Eupatorium sp. (joe-pye-weed) 10/1/96
Euphorbia maculata (milk purslane)
Euthamia graminifolia (grass-leaved goldenrod)
Gnaphalium obtusifolium (sweet everlasting) 10/1/96
Lespedeza cuneata (Chinese bush clover)
Lespedeza capitata (round-headed bush clover)
Linaria vulgaris (butter and eggs) 10/1/96
Lycopus sp. (bugleweed)
Lythrum salicaria (purple loosestrife)
Melilotus alba (white sweet clover) 10/1/96
Oenothera biennis (common evening primrose)
Plantago major (common plantain)
Polygonum sp. (tearthumb) 10/1/96
Polygonum sp. (white knotweed) 10/1/96
Polygonum scandens (climbing buckwheat)
Polygonum cespitosum (cespitose knotweed) 10/1/96
Prunella vulgaris (self-heal) 10/1/96
Rudbeckia hirta v pulcherrima (black eyed Susan)
Rumex sp. (dock)
Silene latifolia (white campion) 10/1/96
Solidago caesia (blue-stem goldenrod) 10/1/96
Solidago spp. (goldenrods) 10/1/96
Taraxacum officinale (dandelion 10/1/96
Trifolium arvense (rabbit foot clover)
Trifolium pratense (red clover) 10/1/96
Trifolium repens (white clover) 10/1/96
Typha latifolia (broad-leaved cattail)
Verbascum thapsus (common mullein)
Verbena urticifolia (white vervain)
Veronica officinalis (common speedwell)

Rushes and Sedges:
Carex lurida (sack sedge)
Cyperus strigosus (umbrella sedge)
Juncus effusus (soft rush)
Juncus tenuis (path rush)

Arthraxon hispidus? (arthraxon grass)
Dactylis glomerata (orchard grass)
Digitaria sp. (crabgrass)
Eleusine indica (goose grass)
Microstegium vimineum (Japanese stilt grass)
Panicum clandestinum (deer-tongue grass)
Poa compressa (Canada bluegrass)
Schizachyrium scoparium (little blue stem grass)
Setaria sp. (foxtail grass)
Tridens flavus (purple top grass)