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Old Furnace State Park (Ross' Cliffs)

539 South Frontage Road/81 Ross Road

Old Furnace State Park (also known as Ross' Cliffs) is a 314-acre State of CT owned forestland. Hike the 4 miles blue-marked trail through a hemlock forest, along Half Hill Pond and up to stunning views that overlook eastern Killingly and Rhode Island at the top of Ross' Cliffs. The cliffs tower 200 feet over Half Hill Pond and give you an uninterrupted view over the eastern half of the town of Killingly and into Rhode Island.

The cliffs have a long climbing history.    The AMC (Appalachian Mountain Club) climbed here in the 1950s as evidenced by the ring pitons on some of the routes. There is no conclusive information as to who first climbed many of these routes despite claimed first ascents. 

The cliffs range from 30 to 85 feet in height and in total are about a quarter mile long. There are four main areas: the Parking Lot Wall, the Party Wall which is easily identified by its large roof, the Orange (AKA Big Wall) which is the tallest at 85 feet high, and the North End.

​Other activities include boating, fishing and hiking. Leased pets are welcome to enjoy the outdoors with you.

Old Furnace State Park contains a mixture of deciduous and evergreen forest trees that are typical in much of Eastern Connecticut. Stone walls and other relics show that farming and industrial activities have taken place, resulting in the second growth forest and man-made ponds that are visible today.

The most notable tree throughout the year is the Canadian (Eastern) hemlock. These majestic evergreen trees are found in many spots along the trail and the cliffs and can be identified by their flattened needles, small cones and dark cinnamon-brown bark. Unfortunately, the damage of a non-native insect, the hemlock woolly adelgid, is very evident in the park. The feeding activity of the hemlock woolly adelgid causes severe thinning and stress on the hemlocks. Other evergreen trees include two species of pine. The most common pine is the eastern white pine which bears soft blue-green needles and long narrow cones.

A less common species is the pitch pine which grows in a few places along the edge of the cliff. The pitch pine has stiff, dark green needles and rounded cones which cling to the branches. Pitch pine is more common in coastal areas, but this tree is able to adapt to the poor growing conditions at the edge of the cliff.

Deciduous forest trees throughout the park include various species of oak, birch, beech, maple and hickory. Common understory shrubs include Witch Hazel, blueberry and mountain laurel.

Several streams, wetlands and man-made ponds can be found along the trail. They contain an interesting mix of native plants including skunk cabbage, cattails and waterlilies. Unfortunately, several invasive plants have colonized the ponds, including phragmites and purple loosestrife. Phragmites is very easy to find because it looks like a large scraggly corn plant which has formed very dense groups along the shoreline.

Invasive plants are a concern at all of our ponds in Killingly. Once established they are very hard to eradicate and will crowd out the native vegetation. To help prevent the spread of invasive plants you should clean weeds off your boat when you exit the water and wash your boat when you get home. You can read more at the Connecticut Invasive Plant Working Group web site.

History of Old Furnace

Originally a Town Park in 1909. Old Furnace State Park was the site of an iron furnace during the 1830’s and 40’s. Through the efforts of Reverend Charles Hutchinson, Jr., the Danielson Methodist minister who was then serving in the Connecticut Legislature, it was made a State Park in the early 1940’s. Although remnants of the stone furnace are still visible adjacent to Fall Brook, extensive landscaping during the beautification of the park destroyed many of the features.

The Furnace

Numerous small iron furnaces were constructed in the Northeast during the eighteenth century. Most had similar shape and basic method of operation. Iron ore frequently found in swamps and bogs, fuel; often charcoal from nearby timber stands, and flux such as limestone or a gabbro rock were fed into the top of the furnace.


Blasts of hot air from enormous water powered bellows fanned the fire. Molten iron was either hardened into long cast-iron bars called sows or it was immediately poured into molds and cast into a variety of products. The slag produced during the operation was frequently disposed of in a nearby river.

Powered by an overshot wheel, the furnace converted iron ore to molten iron which was then cast for multiple uses. The 1830’s saw a number of small cotton mills being established in Killingly. This period also marked the peak of the furnace operation so it was thought that much of the finished product from the furnace was utilized in the construction of mill machinery. More efficient technology and he completion of the railroad through the present day Danielson in about 1840 hastened the demise of the furnace.


Click here for a printable brochure and trail map of Old Furnace. 

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