This 423-acre parcel of land comprises the largest single acquisition by Nassau County of New York City watershed property. The preserve is divided into three sections bounded by major roadways. The southern section, from Merrick Road to Sunrise Highway, contains the most diverse and ecologically valuable lands. Freshwater swamps, marsh, stream, lake and sandy-bog area provide habitat for many rare and endangered Long Island plants, including orchids, carnivorous sundews and bladderworts. The longest hiking trail in Nassau County, the Nassau-Suffolk Greenbelt Trail, begins at Merrick Road and Ocean Avenue and continues through the length of the preserve, ending at Cold Spring Harbor. Freshwater fishing is available in several of the lakes and streams (license required).
In December 2006, the Peter J. Schmitt Massapequa Preserve was named "Best Nature Preserve of Long Island " by Long Island Press, the weekly newspaper.