Marshall Field III bought the property in 1921 and had an estate house built in 1925, one of the largest estates of the Gold Coast mansions.[8] Field named the property "Caumsett", after the Matinecock tribe's original name for the peninsula meaning "place by a sharp rock".[1][9]
The 1,426-acre (5.77 km2) Marshall Field III estate was purchased by New York State for $4 million on February 3, 1961, and became a state park.[3] The former estate was listed on the National Register of Historic Places in 1979.[5]
The historic buildings within Caumsett State Historic Park Preserve are used for a variety of activities; former polo barns are used for equestrian education and services, while other buildings host environmental education programs and the Lloyd Harbor Historical Society.[1]
Much of the remainder of the park is maintained as a nature preserve, with a focus on conservation of bird habitat. The "Caumsett Bird Conservation Area" was established in 2006 and comprises approximately 1,255 acres (5.08 km2) of the state park, two-thirds of which is forested. The remainder includes a variety of habitats, such as salt marsh and maritime beach. The designated area protects high-quality habitat that supports breeding populations of several species listed as threatened or endangered in New York State, including piping plovers, common terns, and least terns; many additional migratory species also make use of the protected landscape.[12]
The park allows for recreation such as horse-riding, fishing, jogging, hiking, biking, and cross-country skiing. Scuba diving is also allowed by permit.[1]
^ ab"Section O: Environmental Conservation and Recreation". 2014 New York State Statistical Yearbook. The Nelson A. Rockefeller Institute of Government. 2014. Table O-9. Archived from the original on September 24, 2015. Retrieved January 31, 2016.