Places We Protect


New York

A rocky shore looking out onto Gardiners Bay.
Mashomack Preserve Mashomack Preserve on New York's Long Island. © Harold E. Malde

Enjoy the natural wonders of our 11 miles of coastline and acres of creeks, woodlands and fields.



NOTE: Mashomack’s trails are open everyday from now until January, and then open weekends-only in January.

See what's happening at Mashomack! You can:

Edged in white by 11 miles of coastline, Mashomack on Shelter Island is considered one of the richest habitats in the Northeast. Just 90 miles from New York City, the preserve covers over 2,350 acres of interlacing tidal creeks, mature oak woodlands, fields, freshwater marshes and underwater lands.

Mashomack has a rich mix of human and natural history. This ancestral land of the Manhanset peoples has housed generations of farmers, fishers and those seeking refuge from the constant bustle of life. Few know that the preserve was once a hunt and game club, and even fewer know that it was nearly transformed into housing developments more than once. Thankfully, The Nature Conservancy, together with the residents of Shelter Island and Long Island, was able to pull together a last-minute effort to save this "Jewel of the Peconic."



Everyday from now until January, open weekends-only in January.


Trails open dawn to dusk, seven days a week. Visitor Center bathrooms open 8 a.m. to 5 p.m., seven days a week, and Visitor Center exhibits open 10 a.m. to 3 p.m., Thursday through Saturday. (Trails will be closed weekdays for the month of January).


2,350 acres

Electric Vehicle Charging

Charging for Rivian electric vehicles is available at this preserve.

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  • Mashomack is open from dawn to dusk, seven days a week. During or following severe weather we may need to close unexpectedly. If the gate is closed, the preserve is closed. Please do not enter the grounds.

    Here are some things to keep in mind: 

    o   Trails open dawn to dusk, seven days a week

    o   Visitor Center Bathrooms open 8 a.m. to 4 p.m., seven days a week

    o   Visitor Center Exhibits open 10 a.m. to 3 p.m., Thursday thru Saturday

    o   Mashomack trails are open weekends only for the month of January

  • Birds: Since 1980, over 200 species of birds, including 79 nesting species, have been recorded at Mashomack Preserve. No matter what season or time of day you decide to visit, you’re sure to witness something amazing.

    In the summer, look for towhees in the understory, scarlet tanagers and Baltimore orioles in the canopy, and red-tailed hawks along the edges of open, grassy meadows. In the fall, Mashomack serves as a popular migration stopover point for many birds. Black duck, Canada geese, hooded mergansers and other waterfowl winter in our salt marshes and surrounding bays.

    Together with nearby Gardiners Island, Mashomack also supports one of the East Coast's largest concentrations of nesting osprey. The coastal areas and salt marshes are great places to view other birds as well, such as great blue herons, great and snowy egrets, green herons and black-crowned night herons.

    Animals: Mashomack’s many habitats harbor a plethora of animal life. Painted turtles basking on a sunny log or spring peepers chirping their amorous intentions may be found in the freshwater wetlands, along with a shy muskrat. A summer’s day is alive with the sights and sounds of insects: monarch and swallowtail butterflies, dazzling dragonflies, or buzzing cicadas. The common grey squirrel and cheeky chipmunk are almost always sighted, while occasional reports of a black racer or other harmless snakes also surface.

    Salt marshes shelter a multitude of marine species including clams, blue claw crabs, and a variety of fishes. The night brings little brown bats and moths, including the beautiful luna and rare Imperial. Other nocturnal creatures may leave footprints, scat, or rubbings to signal that a fox, raccoon, or deer passed by.

    Plants: The only natural community of its kind on Long Island, the Pine Swamp Complex is comprised of plants rooted in a floating mat of sphagnum moss. Probes have found organic accumulations ten feet thick dated to be 3,900 years old. Fringed by water willows and a diverse shrub layer including swamp azalea, highbush blueberry, white alder, winterberry and mountain holly, the swamp also includes a stand of white pines that shelter two state-protected orchids-the whorled pogonia and the pink lady slipper. The Usnea lichen grows on shrubs and trees here, attracting ruby-throated hummingbirds, which use the lichen in their nests.

    In accordance with the Department of Justice’s amended regulation implementing Title III of the 1990 Americans with Disabilities Act (ADA) regarding Other Power-Driven Mobility Devices,” Mashomack has completed an assessment of our public areas and trails. While some types of OPDMDs can be accommodated, there are necessary restrictions on their use.

    • Visitor Center: Please note that as of May 2021, Visitor Center and restrooms are temporarily closed. The Harman Hawkins Visitor Center at Mashomack was updated in 2004 to provide universal access to all public spaces. The main entrance features direct access from the parking area trail to the front porch. The relatively open space floor plan includes ~36” doorways and displays are built for comfortable viewing from wheelchairs. The two public toilets are both accessible (wide doors, large area for wheelchairs, comfort height commodes and grab bars). An ADA-compliant ramp leads from the front porch to the patio and trail head area. The Education Building is also accessible via a ramp.
    • Picnic Area: As of spring 2021, new ADA-compliant picnic tables are available. Please remember to pack it in and pack it out (don’t leave trash behind).
    • Boardwalk: The boardwalk at the entrance of Mashomack is fully compliant with the forest service recommendations and standards for accessibility.
    • Joan C. Coles Trail: First opened in 2000, The Joan C. Coles Memorial Trail (roughly 1 mile in-and-out) is a barrier-free trail that provides scenic views of the preserve’s stunning natural features, amenable to wheelchairs and strollers.
    • Manor House: Please note that as of May 2021, Manor House is temporarily closed. Mashomack’s Manor House is a fully restored 19th century summer estate, now used as a conference facility and for local community gatherings. It is fully accessible with an exterior ramp for entering and exiting, an accessible restroom and an elevator to the second floor to an accessible bedroom and bathroom.
  • Mashomack’s Environmental Explorers program, running annually for over 30 years, is a summer favorite on Shelter Island. Kids ages 8-12 spend four days exploring our changing environment while learning all about nature in a hands-on, fun-filled way through hikes, paddles and adventures galore. Mashomack’s amazing fields, forests and waters also provide inspiration for participants to become environmentally conscientious citizens. All three sessions of our program this summer are now filled but keep an eye on as we announce fall programming across our preserve network.

Trail winding through green meadow with a blue sky.
Mashomack's Magic One of the many trails winding through our Mashomack preserve on Shelter Island. © Charles Gleberman

A Brief History of Mashomack

Shelter Island was originally inhabited by the Manhansets, Native Americans who were part of the wide-spread Algonquin culture. In 1653 Chief Pogatticut, sachem or "chief" of the Manhansets, deeded all of Shelter Island to Nathaniel Sylvester. Sylvester, a sugar merchant from Barbados, established a Quaker refuge on the island.

In 1693, Giles Sylvester, Nathaniel's son, sold Mashomack to William Nicoll I, starting a 230-year "reign" of the Nicoll family at Mashomack. The Nicolls were early settlers in the Islip area. What is now known as Mashomack was originally called Sachem's Neck (the main body of the preserve) and Mashomack referred only to Mashomack Point.; Mashomack means "where they go by water" and the point was probably an island before a narrow neck formed, connecting it to the rest of the peninsula.

William Nicoll II was the first full-time resident of Mashomack. William II deeded Mashomack to William III who farmed the land with his family. Over the years the property was divided among members of the Nicoll family. Turn-of-the-century notable Nicolls include "Miss Annie" Nicoll, who farmed the still-open fields in the center of the preserve. Dr. Sam Nicoll, her brother, built the Bass Creek Cottage now known as the Manor House.

By 1908, nonresident Nicoll heirs had begun selling their portions of Mashomack. F.M. Smith (of 20 Mule Borax fame) was one of the buyers and may have built the building now used as the Visitor Center.

In 1925 Otto Kahn, a wealthy German financier, bought Nicoll family holdings and other portions that had been previously sold, reestablishing the integrity of the tract for a real estate investment. Fortunately, due to the Stock Market Crash of 1929, his development scheme never materialized.

In 1934, the Gerard real estate combine purchased Mashomack from Kahn's estate. The property was leased to several fish and game clubs. Of the hunt clubs which have used the Mashomack property over the years, the most well remembered is the Mashomack Fish and Game Club. Most members were wealthy Long Island or New York City folks who joined the Club to hunt pheasant, duck, or deer. An occasional fox hunt, complete with hounds and horses was also held. The two fields in the center of the preserve were converted into a skeet range and tennis court. The well-appointed Manor House served as the Lodge, with delicious French cuisine prepared for the members. During the Club's residence, a scheme emerged to develop Mashomack into an exclusive housing area. A golf course, marina, and beautiful waterfront homes were planned, and investors for the project were secured. Luckily, the development scheme folded in 1979.

It was at this point, after years of patient waiting and careful planning that The Nature Conservancy (TNC) stepped in and was able to secure Mashomack. Since the 1950s, the Conservancy had expressed hopes of preserving Mashomack because of its population of the then state endangered osprey and rare plants. The Gerard family (Aeon Realty) and The Nature Conservancy came to an agreement in 1979. In order to protect Mashomack, the Conservancy would have to buy all assets of Aeon Realty at a purchase price of $10.6 million.

The assets included:

  • 6 Brownstone Houses in New York, NY
  • 2 Warehouses in Miami, FL
  • Oil & Gas Fields from Louisiana to West Virginia
  • Mashomack, 2,039 acres on Shelter Island, NY

The Gerards allowed The Nature Conservancy to get contracts of sale on the first three assets which sold for $5.5 million. The Conservancy then mounted largest fundraising effort in its history to purchase Mashomack.

On January 14, 1980, The Nature Conservancy took title to Mashomack with the support of 1700 Shelter Islanders and Nature Conservancy members, foundations, and corporations nationwide.

For more details on Mashomack's history, see Muriel Porter Weaver's book, Where They Go By Water, available in the Manor House library.

Clean Water Septic Upgrades

In Suffolk County, where Mashomack is located, nitrogen pollution from more than 370,000 septic systems and cesspools is the primary cause of harmful algal blooms (HABs), including red tides and blue-green algae outbreaks. The septic systems at The Nature Conservancy’s 2,350-acre preserve were part of the problem. Like virtually all of the septic systems on Long Island, Mashomack’s were never designed to treat nitrogen in wastewater.

“Just like in other places, these cesspools and septic systems were installed long before we understood the impact conventional systems could have on our ecosystems,” says Nature Conservancy Marine Scientist Christopher Clapp. In fact, the nitrogen pollution and HABs that result are linked to beach closures, shellfish die-offs and the deterioration of estuaries and coastal marshes, which serve as nurseries and habitat for 65% of our recreational and commercial fish species and help buffer increasingly dangerous and more frequent ocean storms.

Now, instead of contributing to the problem, Mashomack is modeling the solution, with four new, clean-water septic systems that treat wastewater nitrogen onsite. Three of these new systems will eliminate approximately 80% of the nitrogen they process. The fourth will do even more: With a pressurized, shallow drain field, it will eliminate almost all of the nitrogen, as well as pharmaceutical residues, chemicals from personal care products and chemicals of emerging concern. These systems come thanks to the Shelby Cullom David Charitable Fund and the Knapp-Swezey Foundation, which generously underwrote the costs.

“The Nature Conservancy has been a leader in policy solutions to the problem of nitrogen pollution from septic systems,” says Clapp, who notes the organization's work with elected officials to fund and scale up septic system replacement programs and legislation. “Now, I’m happy to say, we’re able to be a leader on the ground, too.”

A shallow ditch with two, long parallel black plastic conduits in it.
Cleaning Power A pressurized, shallow drain field helps the fourth septic septic system go above and beyond, eliminating almost all of the nitrogen along with other harmful chemicals. © Rebecca Kusa/TNC
A large white septic tank suspended over the ground by a crane, with a worker guiding it into place.
Modeling the Solution Updating to the new septic systems, a unit of which is pictured here, is a critical way to address nitrogen-pollution-fueled harmful algal blooms. © Christopher Clapp/TNC
Cleaning Power A pressurized, shallow drain field helps the fourth septic septic system go above and beyond, eliminating almost all of the nitrogen along with other harmful chemicals. © Rebecca Kusa/TNC
Modeling the Solution Updating to the new septic systems, a unit of which is pictured here, is a critical way to address nitrogen-pollution-fueled harmful algal blooms. © Christopher Clapp/TNC

Find More Places We Protect

The Nature Conservancy owns nearly 1,500 preserves covering more than 2.5 million acres across all 50 states. These lands protect wildlife and natural systems, serve as living laboratories for innovative science and connect people to the natural world.

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