A History of the Great Swamp
This article was written by FROGS members Jill Eisenstein and Judy Kelley-Moberg.
The Great Swamp has a unique history. Its presence and resources have molded the people that moved along its shores through the centuries. But what molded the swamp?
Over a billion years ago, the Hudson Highlands were a towering mountain range of folded rocks formed from the edge of an ancient sea. Many seasons and great ice sheets wore them down to the rounded hills we see today. The ridges are made of hard gneiss and quartzite, but softer marble or calcium carbonate lies beneath the valley floor. The marble makes the water in the Great Swamp “sweet” (of a higher pH) rather than acidic, creating some unusual habitats for plants and animals.
Geologists have discovered evidence of great crustal changes that have taken place over billions of years, shaping and reshaping the surface of the earth. As the crust moved, continents moved about, ancient oceans were created only to vanish again.
On what is now the Great Swamp, layers of sand, silt, mud and marine carbonates deposited in the ancient seas were compressed and cemented into sedimentary rocks — shale, sandstone, and limestone. Over a billion years ago, tremendous heat and pressure from a continental collision folded up the sedimentary rocks and changed them into tough, dense metamorphic rocks – – marble, schist, quartzite and gneiss — making the mountains of the Hudson Highlands and the Adirondacks. The tough, resilient gneiss with swirling bands of white quartzite are visible in the eroded roots of the ancient mountains surrounding the Great Swamp.
Another collision about 450 million years ago created the Taconic Mountains that were pushed right up against the eastern end of the Highlands. These two events created the long north-south valley that contains the Great Swamp.
The softer marble bedrock remained on the valley floor and became the bottom of the Great Swamp. As the water there today flows through and over the marble, its chemical makeup becomes more basic. Areas in the Great Swamp support rare and endangered plants that require very low acidity and low nutrient levels.
The last geologic event to shape the valley was the advance and retreat of the Wisconsin lobe of the Continental ice sheet. The ice, a mile thick at the Canadian border, moved southward at the rate of about a foot per day for 10,000 years. It rounded out the valleys and ground down the hilltops. It plucked up huge boulders and pushed piles of sediment that it would leave behind when it melted. When the ice sheet retreated from southern New York beginning about 12,000 years ago, the land resembled the Arctic tundra. Large chunks of ice and piles of sediment blocked the valleys, collecting the melt water in long shallow lakes. Clay beds in the Great Swamp tell us that for a period of time it was a post-glacial lake whose still waters allowed the fine clay silt to settle out.
As the ice melted, it began to flow toward the sea. A rock ridge near what is now Pawling sent the waters of the Great Swamp draining in two directions – north through a series of riverbeds to Long Island Sound and south through a channel of the Croton River to the Hudson.
Ice free corridors along the ridgelines and the shrubby vegetation attracted herds of Ice Age mammals such as wooly mammoths, mastodonts, and musk ox. Human hunters followed, and historians have found the spear points designed to hunt the huge beasts.
Civilization and the Great Swamp
For thousands of years after the Ice Age, a gradual warming trend continued. Sea levels rose. Deciduous forests of oak, maple, beech, hickory, and chestnut replaced the tundra and tiaga plants. The Great Swamp began to evolve into what it is today, a diverse wetland composed of rivers, marshes, shrub swamps, fens and forested floodplain. It abounded with fish, turtles, amphibians, mammals and waterfowl and the early people that lived along its edges found it an abundant source of food. They hunted and gathered in the highlands and traveled to the shores of both Long Island Sound and the Hudson River to gather shellfish and fish during spring runs. Only stone tools and pottery shards remain to mark the locations of their campsites and villages. Daniel Nimham, the last sachem of the Wappinger People of the Hudson River Valley and a hero in the American Revolution, maintained that land grabbers during the time of the French-Indian War had taken tribal ancestral lands in eastern New York from his people. No doubt, the abundant wild food made the area attractive.
Dutch merchants in New Amsterdam in the 1600s were interested in trading with the native people not for food but for valuable beaver pelts, as the pelts were all the rage in Europe. The Great Swamp’s beaver population was trapped out by the late 1600s.
The European Settlers
Attracted by the rich farmland, European settlers began to filter in to the uplands around the Great Swamp in the early 1700s. The Great Swamp determined the early settlement patterns. Settlers came over the hills from Connecticut on “Indian trails”, avoiding the Great Swamp for fear of “Swamp fever”. The Great Patent Road, now Route 22, was the major north-south highway running along the eastern edge of the Great Swamp.
The Great Swamp, stretching for 20 miles north and south, and almost 2 miles across at its widest point, meant only a few readily passable east-west routes. During the Revolutionary War, General Washington headquartered near Fredericksburg, now Patterson, which had a bridge over the East Branch Croton River and was the primary crossing point. From Fredericksburg, one could travel eastward to Danbury and the coast, south to Bedford and Peekskill, west to Fishkill and the Hudson or north into Massachusetts.
By the 1800s the farmers had cut down the forests, crisscrossed the land with stone walls, and developed upland pastures for sheep and cattle with lowland fields producing grain to feed them. Vast numbers of cattle and sheep were fattened on the rich pastureland before being driven down Route 22 to the markets in New York City. Small hamlets grew up around crossroads and the mills and tanneries on the tributaries feeding the swamp.
Though they also hunted and fished in the swamp, some of the farmers thought they might do better without it. William S. Pelletreau, in his History of Putnam County (1886) mentions plans of ambitious farmers who hoped to drain the swamp to gain rich farmland.
Nineteenth century farmers had the idea that they might drain the Great Swamp to gain rich farmland. They never found the funds to drain it, but some turned to profits from the Great Swamp’s other natural resources: marble, clay and ice.
The low grade marble that forms the floor of the Great Swamp, locally referred to as limestone, was quarried in large blocks up to the turn of the 20th century and can be seen in the foundations of homes and churches in Patterson. The “limestone” was also crushed and heated in local lime kilns to produce the lime used in mortar, whitewash and fertilizer. Limestone was also used in blast furnaces to separate the impurities from the iron ore mined throughout the Hudson Highlands. The Dover Furnace still stands near the Great Swamp floodplain in the Town of Dover, and a deep open pit quarry in the village of Patterson still produces crushed limestone used as a road base, now called “Item 4”.
As shallow lake water receded over the centuries, the clay that had settled out in post-glacial times was exposed. In the 1830’s William Merritt used the ancient clay beds near Croton Lake, now called Ice Pond, to produce bricks.
Ice Pond and its drainage forms a major sub-basin in the south flow of the Great Swamp. A testament to the reluctance to build across the “impenetrable” swamp, railroads built north/south lines on raised beds along the edges. The MetroNorth tracks were built as the New York and Harlem Railroad in 1848 and ran along the western shore of Ice Pond. In 1881, the now-inoperable New Haven/Maybrook Line bridged the Hudson, and crossed over its New York City track on overpasses and a trestle-bridge in Towners to travel down the east side of Ice Pond to Danbury.
In the late 1800’s a huge commercial ice house was built on the western shore of Ice Pond, sending tons of ice to New York by rail and giving Croton lake its new name of Ice Pond.
Old hamlets were bypassed as new businesses and hamlets grew up around the railroad stations. At first, the railroads were a boon to local dairy farmers, who could ship their milk on refrigerated rail cars to the city. But farming in the area eventually became unprofitable; the local farmers could no longer compete with the cheaper products carried by rail from further north.
The location of the rail lines may be one of the reasons an 1883 plan to impound the south flow of the Great Swamp never became a reality. In preparation for the reservoir proposed to create additional storage for New York City’s Croton Reservoir System, many houses in the Village of Patterson and nearby Towners were moved or destroyed. But moving the rail lines probably presented insurmountable difficulties. In the end, the City decided to tap the Catskill watersheds instead.
The Great Swamp: A Place of Change
Since its formation over ten thousand years ago on bedrock formed billions of years before that, the Great Swamp has been changing. But the changes seem to be accelerating. The Great Swamp has molded civilization, but civilization is also impacting it.
A testament to these changes is Pine Island, a rocky ledge covered in hemlocks, rising about 200 feet above floodplain south of Patterson. From the 1700s until the return of beavers in the late 1900s, the swamp surrounding the island was a treed swamp, thick with red maples. Because of beaver activity, it is fast becoming an open marsh. Until the Chestnut Blight of the early 1900s the island contained thick stands of chestnut trees. Now, but for a few hardwoods, the trees on the island are primarily hemlock. But that, too, is changing; the deadly Hemlock wooly adelgid (Adelges tsugae) has been found on the island.
In 1935 Leroy Smith, Willis Watkins and Walt Denton built an 8 by 11-foot hunting cabin on its north end and called it “Hawk’s Rest”. It had two bunks, a wood stove, and a skylight that opened to shoot crows. Through WWII and into the 1950’s the cabin was “a haven where nature moved in its predictable pace outside of time and world events,” wrote a local historian. Continuing to move in its predictable pace, nature has since removed all but small traces of the abandoned cabin. Musings and sketches about life in the swamp between 1941 and 1947 were recorded by its visitors in the “cabin chronicles” and they depicted a place of refuge and rest as well as an outdoor classroom for adventurers paying attention. Thoreau might have enjoyed the journal. It was recently donated to the Patterson Historical Society by a child and grandchild of Smith.
Through the 1940s and ’50s coastal wetlands and freshwater swamps like the Great Swamp were considered stinky wastelands and a hindrance to the march of progress. They needed to be filled in to make room for development right up to the edge of navigable water. It wasn’t until the environmental movement of the late ’60s that an awakening began about the importance and function of wetlands. The Great Swamp suddenly offered new natural resources. Not marble, clay or ice, but flood control and clean water. Not the abundant hunting and fishing of the 1600s but protected flyways for waterfowl migrations and habitats for rare and endangered species of plants and animals. When a section of the Great Swamp in Patterson was threatened in 1989 by a Putnam County dump project, the local community, friends like Pete Seegar and bigger environmentally conscious groups, fought to protect it.
The Friends of the Great Swamp (FrOGS) was formed in 1990 and worked closely with the Nature Conservancy which sponsored scientific studies, publishing The Great Swamp: A Watershed Conservation Strategy in 1999. FrOGS continues to educate the public about the value of the Great Swamp in cleaning and storing water, preventing floods, providing habitat for plants and animals, and recreational opportunities.
Today, the Great Swamp has become a destination for paddlers seeking Hudson Valley waterways to enjoy. Its edges attract hikers and rock climbers. Paddlers see beaver, muskrats, turtles, Great Blue herons, red-wing blackbirds, and birds of prey on any given day. Hikers see rare and beautiful wildflowers, rock formations, and vistas. It is considered one of the most scenic wild places in Putnam County. Will these paddlers introduce invasive plant life brought from other waterways? Will the march of progress along the uplands send too much pollution down the slopes? What will happen as the climate continues to change?
One thing seems certain. Changes will continue in the Great Swamp, and its protection is more important with each passing year.