Grater Woods is an extensive tract of forest with interspersed wetlands and has several entrances.

The most widely used by recreational hikers is located in the upper parking lot of Merrimack Middle School, within walking distance of multiple trailheads, the School Loop being the trail directly next to the kiosk. If using this entrance, it is recommended you go on weekends, as school is not in session, otherwise, check-in at the main office is required. Many trails are long, winding, and frequently intercept each other, so a trail map is helpful. At a birder’s pace, all trails take a substantial time investment.

The most productive area for birds is that of the Gateway Trail, accessed through the entrance at Beebe Lane (or Conservation Drive, but there is no parking lot there). Joined with the Drilled Rock Trail to make a loop around a large beaver pond, this circuit encompasses multiple habitat types and is especially active in late spring when a diversity of migrant warblers abound.

From a birding standpoint, this site is under-explored and offers a lot of ground to cover. Parts of the property not associated with the Middle School are frequented during the hunting season, so wear orange during this time.

Blue-headed Vireo, Barred Owl, Scarlet Tanager, and Great-crested Flycatcher are common on the Gateway Trail, along with Common Ravens, Eastern Towhee, and Brown Creeper on the Drilled Rock Trail. In fall and winter, sparrows can be found in the weedy edges and openings, and many late birds such as Hermit Thrush, Yellow-rumped Warbler, and Ruby-crowned Kinglet linger here. Winter Wrens are seen along the marsh edges, and winter finches like Pine Siskins feed in the many birch trees lining the open areas. The path leading from the Middle School parking lot up to the Gateway Trail entrance has a weedy cover that often shelters sparrows and warblers, and is worth a check.

Charles Edwin Grater, born 28 May 1827, purchased the land known today as the Grater homestead on South Grater Road in the mid-1800s. Today, the Grater Woods Forest is a contiguous 480-acre parcel of property formed through land acquisitions by the Merrimack Conservation Commission. The property is comprised of several parcels inclusive of a 32-acre easement of protected open space owned by the Merrimack School District. Due to the forest's size, woodland diversity, the number of wetlands, and impact on wildlife and water resources, the Grater Woods Forest is listed as a top priority for conservation in the 2002 Town of Merrimack Master Plan.

Much of the property was cleared for pasture in previous centuries and has been logged several times. Many old logging roads and newly managed trails form the basis of today’s trail network used by hikers, bikers, runners, hunters, snowmobilers, horseback riders, skiers, ATVers, and bird watchers. The trail network covers the majority of the property and continues to expand. The Grater Woods Forest now serves as an important habitat for wildlife as well as providing recreational benefits to town residents.

The forest consists of mixed hardwood and softwood trees between 20-60 years of age. The property also includes a variety of streams, ponds, swamps, and numerous wetlands totaling approximately 100 acres. The varied terrain, habitat, and large areas of undisturbed open space have encouraged a wide variety of wildlife to thrive on the property. Contained within this parcel are habitats for beaver, fisher, deer, moose, and turkey as well as unique features such as vernal pools, beaver ponds, and glacial erratics. The Grater Woods Forest, together with other forests in the region, provides a wildlife corridor (greenway) that allows animals to freely migrate in and out of the forest.