This Massachusetts wildlife refuge hides 50 WWII bunkers in the woods

It’s 20 miles from Boston

Twenty miles west of Boston, a 2,230-acre wildlife refuge spreads across four towns in Massachusetts, and most people driving past it have no idea what’s hiding inside.

Assabet River National Wildlife Refuge covers parts of Sudbury, Stow, Maynard and Hudson, with more than 15 miles of trails cutting through forests, wetlands and a pond with fishing piers.

The whole place is free, open sunrise to sunset every day of the year. But the trails lead past something you won’t find at any other hiking spot in New England.

Families lost their farms to build an ammo depot

The land under this refuge has changed hands in ways most places never do. The Nipmuc people lived here first.

Colonial families later turned it into small farms. Then, in 1942, the U.S. Army seized the entire area by eminent domain to build the Maynard Ammunition Storage Backup Point.

Dozens of families had to leave their homes with almost no warning.

The Army laid railroad tracks, poured concrete, and built 50 bunkers to store ammunition for the war effort.

After the war, the military kept using the site until contamination turned it into an EPA Superfund cleanup project. The Army finally transferred the cleaned-up land to the U.S. Fish and Wildlife Service in 2000, and the refuge opened to the public in March 2005.

Sealed concrete bunkers line the hiking trails

Walk the trails here and you’ll come across dozens of sealed concrete ammunition bunkers from the 1940s, scattered through the forest like something from a forgotten war movie.

Dirt, pine needles and young trees cover their tops and sides now.

The Army built each one with a curved roof designed to push any explosion upward instead of outward. You can’t go inside them, but you can walk right up to several from the trail.

Nothing else in New England gives a hike that kind of edge.

Flat trails wind past old stone walls

Over 15 miles of trails run through the refuge, and about half of them allow biking.

The ground stays mostly flat with almost no elevation change, so the walking is easy no matter your age or fitness level. Winterberry Way, Harry’s Way, Otter Alley and the Tri-Town Trail are the popular routes.

Paths are hard-packed dirt with some paved sections, and they take you through forest, past wetlands, along old stone walls and beside what’s left of colonial-era homesteads.

Fish from two piers at Puffer Pond

Puffer Pond sits at the heart of the refuge with two fishing piers built for catch-and-release. One of the piers is fully accessible for people with disabilities.

Stand at the water’s edge long enough and you’ll likely see great blue herons wading or a kingfisher diving for a meal.

Beyond the pond, the refuge holds a large wetland complex, several smaller wetlands and vernal pools that serve as breeding grounds for dozens of species.

Winterberry Way, Taylor Way and Otter Alley run right alongside the best viewing spots.

The Atlantic Flyway runs right through here

The refuge sits along the Atlantic Flyway, one of the major routes birds follow up and down the East Coast during migration. Mass Audubon has named the area an Important Bird Area for its high diversity of species.

Scarlet tanagers, Baltimore orioles, eastern towhees, American woodcocks and willow flycatchers all live and breed here.

You might also spot warblers, hooded mergansers, belted kingfishers and Cooper’s hawks on a single visit.

The U.S. Fish and Wildlife Service runs long-term breeding bird surveys and hawk watches on site.

Bobcats, beavers and otters call it home

About 70 percent of the refuge is forest, with roughly 476 acres of wetlands filling the rest. That mix creates habitat for white-tailed deer, American beavers, bobcats, foxes, coyotes, otters and minks.

The vernal pools fill with water every spring and draw frogs and salamanders to breed. Wild turkeys, raptors and waterfowl show up throughout the year.

Come in winter and you can read the story of who’s been moving through the woods just by following tracks in the snow.

A bright yellow throat marks a threatened turtle

The Blanding’s turtle has a bright yellow throat and a serious problem: it’s listed as threatened in Massachusetts.

Since 2006, the U.S. Fish and Wildlife Service has worked to build a new population of these turtles right here at the refuge.

Hatchlings come from nearby Oxbow National Wildlife Refuge, and some spend their first year in captivity to give them a better shot at survival.

Over 1,000 Blanding’s turtles have gone into the refuge since the program started. The mix of wetlands and protected upland makes it the right kind of home.

Cedar swamps and glacial kettles survive here

An Atlantic white cedar swamp grows inside the refuge, a habitat type that’s rare in this part of Massachusetts. Dwarf shrub bogs, a sandy-bottom kettle hole pond and open peatlands round out the unusual landscapes.

These spots support plant and animal species you’d have trouble finding anywhere else in the region. The land itself still shows signs of glacial activity, with moraines, an esker and kettle holes shaping the terrain.

The whole refuge also plays a role in the Sudbury-Assabet-Concord Rivers watershed, helping with water quality and flood control.

Snow opens up views the leaves hide

Cross-country skiing is allowed on all trails when enough snow covers the ground, and snowshoeing works anywhere in the refuge.

The bare trees in winter pull back the curtain on wetlands and landscapes that stay hidden behind thick leaves from spring through fall.

Animal tracks pressed into fresh snow give you a way to spot wildlife even when the animals themselves stay out of sight.

The refuge stays open year-round, and every season changes the look of the place enough to make a return trip worth it.

A rail trail connects five towns along the river

The Assabet River Rail Trail runs along the northwest edge of the refuge and connects to it at White Pond Road.

The paved trail links Marlborough, Hudson, Stow, Maynard and Acton along a former railroad corridor, passing views of the Assabet River, old mill buildings and a restored 1921 railroad caboose.

Inside the refuge, a dirt road called Track Road picks up where the pavement ends and works well for mountain biking.

Put the refuge trails together with the rail trail and you can cover nine miles or more in a single outing.

Thoreau walked this ground in 1851

Colonial history shows up under your feet here. Old stone walls, cellar holes and chimneys from long-gone farms line several trails.

Old Marlborough Road, now a walking path inside the refuge, carried ammunition from Concord to Marlborough during the Revolutionary War.

Henry David Thoreau wrote about walking along the Assabet River through this area in 1851.

The railroad tracks that once linked all 50 bunkers are gone now, but their straight paths survive as some of today’s trails. What the Army closed off, nature has slowly taken back.

Explore Assabet River National Wildlife Refuge in Massachusetts

You can reach the refuge at 680 Winterberry Way in Sudbury, Mass. The whole place is free and open daily from sunrise to sunset, every day of the year.

Three parking areas spread the access around: Hudson Road in Sudbury, White Pond Road in Stow and Old Marlborough Road in Maynard.

A visitor center sits on Winterberry Way, and a Friends group runs a nature store on select days. Leave the pets at home, though. Dogs, horses, swimming, boating, camping and motorized vehicles are all off limits.

This article was created with AI assistance and human editing.

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