Saugus Iron Works National Historic Site

Saugus Iron Works National Historic Site

Natural World

Saugus Iron Works National Historic Site preserves the cultural and natural history of the first successfully integrated manufacturing facility for the production of cast and wrought iron in North America. The historic structures of the Iron Works are nestled along the banks of the Saugus River, an important natural resource for newly settled families and workers to the area during the 17th century.

The tidally influenced Saugus River is also a principal natural resource for a wide variety of plants, animals, and other organisms that depend on the river, riparian woodlands, and surrounding marshes as an important habitat.

Saugus Iron Works National Historic Site is filled with plant and animal diversity. The site contains over two hundred species of plants, thirty five species of birds, ten species of mammals, four species of reptiles and amphibians, and at least four species of fish. The site also has numerous species of invertebrates, such as insects, spiders, and crustaceans, an important food source for larger wildlife residing along the Saugus River.

Natural Features & Ecosystems

Saugus Iron Works National Historic Site contains many types of natural features. The most dominant of these features is the Saugus River, which flows through the middle of the historic site.  The Atlantic Ocean, which is located approximately three miles downriver, plays an important role in the habitat and biodiversity within the Saugus River by regulating the level of salts and minerals in the water through changes in the tides.  

Surrounding the Saugus River and its floodplain are small estuarine wetlands. These wetlands contain many species of  plants that thrive on the mixture of freshwater from the Saugus River and saltwater from the Atlantic Ocean.

Saugus Iron Works also has a few small patches of riparian woodlands. These woodlands provide additional habitat for plants and animals that are not normally found in other areas of the historic site. Several seeps and springs that feed into the Saugus River are also located throughout Saugus Iron Works.

Environmental Factors

The cultural and natural resources within Saugus Iron Works National Historic Site are important in interpreting the story of how 17th century European settlers adapted their lives to succeed in the building of Colonial America. Today, these resources are under constant threat in many ways.

The Saugus River is perhaps the most significant natural and cultural resource within the historic site, and, in turn, the most sensitive resource to environmental change.  Water pollution, human development, and the introduction of non-native invasive plants and animals have changed this unique river over the last three and a half centuries. Park staff at Saugus Iron Works are working closely with other government agencies and local organizations to monitor the health of the Saugus River and its watershed.

Currently, sixteen species of non-native invasive plants can be found within the historic site.  Phragmites, purple loosestrife, Norway maple, and multiflora rose dominate many areas of the historic site. These invasive plants, along with many others, outcompete native plant species for space, light, and food. This, in turn, changes the biodiversity and habitat of the natural resources here.  The non-native invasive plants found within the historic site today never existed in Massachusetts before the 17th century. The majority of these plants were brought here from Europe and Asia as settlers continued to arrive and develop the land. The historic site is also home to some animal pests, such as carpenter bees and ants. These insects threaten the cultural resources, by damaging the wood of the historic buildings. Park staff at Saugus Iron Works are currently surveying, monitoring, and, if necessary, reducing or eliminating populations of non-native invasive plant and animal species using established pest management guidelines approved by the National Park Service.

Saugus Iron Works National Historic Site contains over 160 species of plants.  Approximately 89 species of these plants are considered native to the area.  Several species of trees can be found along the Saugus River within the riparian woodlands. Examples include white and scarlet oaks, American beech, shagbark hickory, black walnut, black cherry, black willow, red and silver maples, and boxelder. Many of these trees provide food to the native birds, squirrels, and chipmunks by producing seeds and nuts.

At least 27 species of plants are found within the wetland areas surrounding the Saugus River. Many of these plants are common throughout the marsh, such as narrow-leaved cattail. The tall wetland vegetation provides excellent habitat for nesting red-wing blackbirds and other bird species and breeding fish, such as the fourspine stickleback.

Wildflowers are also abundant throughout the year at Saugus Iron Works. Jack-in-the-pulpit, skunk cabbage, jewelweed, goldenrod, and several species of asters can be found throughout the historic site. Saugus Iron Works is also home to three species of fern: sensitive fern, cinnamon fern, and lady-fern.

Nonnative Species

Although Saugus Iron Works National Historic Site contains numerous species of native plants, animals, and other organisms, non-native species can be easily seen within the historic site.  Many of the non-native species at Saugus Iron Works are classified as plants.

In 1996 and 1997, a plant inventory was conducted by the Brooklyn Botanic Garden to determine the plant diversity within the historic site. One hundred and sixty species of plants were identified within Saugus Iron Works. Of these 160 plant species, 59 are non-native and 11 of these 59 species are considered non-native and invasive.

Many species, such as the plants found in the Iron Works House 17th century herb garden, are considered non-native, because these plants are originally from Europe or Asia. However, these herbs are not classified as invasive, because they do not outcompete native plants for sunlight, water, nutrients, and habitat within Saugus Iron Works.  Other non-native plant species, such as Norway maple (Acer platanoides) and common reed (Phragmites australis) are considered non-native and invasive because these plants are able to outcompete native plants. As non-native invasive plants continue to outcompete native ones, the populations and species of native plants start to decline.

In 2003, National Park Service staff conducted a survey of Norway maple, common reed, and other non-native invasive plants within the historic site. The primary goals of this survey were to identify which invasive plant species inhabit the site, determine the population densities of the invasive plant species, and map where the invasive plant species occur within the historic site. The survey identified and mapped 11 primary invasive plant species and listed an additional 31 secondary exotic plant species within Saugus Iron Works. This survey is currently being used by park staff to control and monitor the 11 primary non-native invasive plant species.

Numerous species of amphibians, birds, fish, mammals, and reptiles utilize the Saugus River and surrounding wetlands and riparian woodlands within Saugus Iron Works National Historic Site as an important refuge to thrive and reproduce. Some animals are seen for brief periods, while others make the historic site their home throughout the year.

During the spring, the red-winged blackbirds and mallards prepare their nests within the tall wetland grasses, while the barn swallows return to the Iron Works to begin raising a new generation. In early summer, the snapping turtles lay their eggs, while the muskrats playfully swim in the cool waters of the Saugus River. Great blue herons and black-crowned night herons perch atop the maples and hickories along the winding river in search of the elusive alewife as the Atlantic Ocean tide slowly moves upstream, inundating the wetlands.

As the summer slowly disappears for the year, spotted sandpipers can be seen hopping about the river mudflats while the barn swallows teach their young how to fly swiftly before their long journey south to warmer climates.

Each animal, as well as many others whose stories have yet to be told, is an important part of the complex ecosystem within Saugus Iron Works.


Saugus Iron Works National Historic Site is the home of over 37 species of birds. The more common native bird species found here include the American crow (Corvus brachyrhynchos), American robin (Turdus migratorius), gray catbird (Dumetella carolinensis), yellow warbler (Dendroica petechia), common yellowthroat (Geothlypis trichas), song sparrow (Melospiza melodia), northern cardinal (Cardinalis cardinalis), and red-winged blackbird (Agelaius phoeniceus).  These bird species may be found in all three major habitat types within the historic site. These habitat types are broadly classified into landscaped areas, wetlands, and riparian woodlands.

Saugus Iron Works is also home to three species of non-native birds, including the rock dove or domestic pigeon (Columba livia), European starling (Sturnus vulgaris), and house sparrow (Passer domesticus). These bird species are native of the European continent.

Some of the native perching birds that spark the interest of park visitors include the barn swallow (Hirundo rustica), Baltimore oriole (Icterus galbula), and American goldfinch (Carduelis tristis).

Many species of birds can be seen occasionally within the Saugus River, including the mallard (Anas platyrhynchos), Canada goose (Branta canadensis), black-crowned night heron (Nycticorax nycticorax), great blue heron (Ardea herodias), and belted kingfisher (Megaceryle alcyon).

Saugus Iron Works also has two species of native woodpeckers: the downy woodpecker (Picoides pubescens) and northern flicker (Colaptes auratus).


Two species of amphibians have been seen at Saugus Iron Works National Historic Site, the green frog (Rana clamitans melanota) and the northern two-lined salamander (Eurycea bislineata bislineata). Although it is believed that the green frog does not actually breed within the historic site, this frog can be seen occasionally within the Saugus River wetland and the sluiceways of the Iron Works during the spring.

Unlike the green frog, the northern two-lined salamander has been observed breeding within Saugus Iron Works. These reclusive amphibians frequently seek shelter under logs, stones, and other objects near seeps, springs, and the Saugus River. It is within these sheltered areas that the female salamander lays her eggs.


Presently, three species of reptiles have been identified within Saugus Iron Works National Historic Site, the eastern garter snake (Thamnophis sirtalis sirtalis), the northern brown snake (Storeyia dekayi dekayi), and the common snapping turtle (Chelydra serpentina). These reptiles are pretty elusive and are able to camouflage themselves within the wetland areas bordering the Saugus River.

The eastern garter snake and the northern brown snake can be seen from early spring through summer and fall where they inhabit marshes, woodlands, hillsides, streams, and drainage ditches.

While the garter snake and brown snake can be seen over a long period of time through many seasons, the common snapping turtle makes its appearance for a very short time during the summer. During this period, female snapping turtles slowly emerge from the protective waters of the Saugus River, locate suitable nesting areas in gravel and sand, and lay between twenty and forty eggs before returning to the river.  Many of the eggs are eaten by raccoons before the turtles have the chance to develop; however, the small turtles that do manage to survive quickly find their way back to the Saugus River, where they will mature and reach weights of up to 35 pounds. These turtles, in turn, will repeat the circle of life, ensuring the survival of the species for future generations.


At least nine species of native mammals have been observed within Saugus Iron Works National Historic Site. The most common mammal found here is the eastern gray squirrel (Sciurus carolinensis) where it can be seen daily throughout the year within the riparian woodlands and the landscaped areas surrounding the historic buildings. Two other mammals that are closely related to the eastern gray squirrel can also be seen within Saugus Iron Works, the eastern chipmunk (Tamias striatus) and the woodchuck (Marmota monax).

Several species of mammals depend upon the Saugus River as an important habitat and food source. The muskrat (Ondatra zibethica), raccoon (Procyon lotor), and river otter (Lutra canadensis) can be occasionally seen within the river and surrounding marshes.

Other mammals that have been observed within Saugus Iron Works include deer mice (Peromyscus maniculatus), striped skunks (Mephitis mephitis), mink (Mustela vison), and bats (Chiroptera).


The Saugus River and its tributaries are home to many species of fish. Some are true freshwater species, such as redfin pickerel, white sucker, yellow perch, and bluegill. Other species may be found throughout the year in brackish water estuaries (mixture of freshwater and saltwater) , such as sticklebacks and mummichogs.

Several fish species spend a part of their lives in the ocean. The alewife, blueback herring, and rainbow smelt are anadromous fish. They swim up rivers and streams from saltwater to freshwater from late winter through spring to spawn. In the fall, young fish swim back to the ocean where they mature. The American eel is known as a catadromous fish. They spawn in oceans and their young migrate towards freshwater to feed and mature.

Alewives and other anadromous fish species were an important food source for Native Americans and early European settlers. Early fishermen built weirs or small dams in the river using nearby stones. These weirs helped fishermen capture alewives by the thousands. Fishing quickly grew as a profitable industry from the 17th century through the middle part of the 19th century. Fisherman caught and sold bass, shad, alewives, perch, smelt, and eels. There were so many fish in the river during this time that large quantities were collected in scoop nets. During the early part of the 19th century, fish were routinely caught on the “Cinder Banks” at the head of the tidewater of the Saugus River. The “Cinder Banks” area is now known as the slag pile, a primary feature of the historic landscape at Saugus Iron Works National Historic Site.

Within the last twenty years, two major fish inventories were conducted within Saugus Iron Works National Historic Site.  The first major inventory was completed by Hudsonia, an environmental research institute, in 1989. Hudsonia found four species of fish, including American eel (Anguilla rostrata), four-spine stickleback (Apeltes quadracus), white sucker (Catostomus commersoni), and mummichog (Fundulus heteroclitus). The second major fish inventory was conducted in 2004 by the University of Rhode Island. This study listed eleven species of fish. In addition to the four species previously surveyed by Hudsonia, the University of Rhode Island discovered alewife (Alosa pseudoharengus), brook stickleback (Culaea inconstans), redfin pickerel (Esox americana), three-spine stickleback (Gasterosteus aculeatus), large mouth bass (Micropterus salmoides), white perch (Morone americana), and nine-spine stickleback (Pungitius pungitius). The data provided by these surveys enables the National Park Service staff at Saugus Iron Works to better understand, manage, and protect the various fish species found within the Saugus River watershed.

Additional fish inventory and monitoring projects will continue in the near future. Beginning in the spring of 2005, the National Park Service will partner with the Saugus River Watershed Council, the Corporate Wetlands Restoration Partnership, and the Massachusetts Division of Marine Fisheries to conduct a rainbow smelt (Osmerus mordax) and American eel spawning survey within the river. This project will provide new smelt and eel population and habitat information to state and federal fisheries biologists.