In May 1662, an area of 150 square miles (390 km2) of land, including the island, was sold by the Wangunk tribe to the English settlers for 30 coats.

[3][4] Though little documentation exists today, the Wangunk tribe lived on the island and in the surrounding area before selling it along with the rest of their land.

[3] Records in the late 19th century indicate that the Haddam Island area of the Connecticut River was dredged annually.

[8] The island became a popular recreational area with picnics and private events in the beginning of the 20th century.

[3] Haddam Island State Park is home to a large number of bird species, especially during annual migrations, which make it suitable for birdwatching.