Northwest Conservation Land, to be named Northwest Sanctuary, is located in the northwest section of the City of Nashua, southwest of NH-101A. It is bordered on the northeast and east by Guilford Industries Railroad and commercial and industrial uses along NH-101A, on the north by a small portion of the Town of Merrimack, and on the west and south by the Town of Hollis. The total area of the site is 294.7 acres. The site is predominantly wooded, with approximately thirty acres of wetlands and three thousand feet of shoreline along Pennichuck Pond on the west.

The site is located entirely within the Pennichuck Brook Watershed, which serves as the major water supply for the City of Nashua and serves portions of the Towns of Merrimack, Milford, and Amherst, as well as other customers. It was purchased by the Pennichuck Corporation in 1935 and has remained essentially undeveloped except for limited forest management and logging. The most recent logging activity consisted of selective harvesting and thinning in 2000. Several logging roads remain one of which is used as access to residential property along Pennichuck Pond.