Manresa Island is a former island located in Norwalk, Connecticut, at the mouth of Norwalk Harbor in the Long Island Sound. The earliest name for the landform was Boutons Island, which dates to 1664. By the 19th century, the island had been purchased by John H. Keyser, who lived there and cultivated rare vegetation. He built a causeway in 1860, connecting the island to the mainland of South Norwalk. This gave rise to the name Keyser Island, which was sold to the Jesuits toward the end of the century.

In the 1950s, Connecticut Light & Power constructed a coal-fired power plant on the land. Over the years, the company filled in much of the tidal flats surrounding the island with coal ash, greatly increasing the size of the island from its original 23 acres (9.3 hectares) to 144 acres (58 hectares), and leading to significant ground pollution. In 1972, the plant was converted to burn fuel oil, and an oil spill occurred, damaging the surrounding environment. The plant was sold to NRG Energy in 1999, and was severely damaged by Hurricane Sandy in 2012, leading to its permanent closure in 2013. A portion of the land today is an undeveloped and ecologically important marine habitat. (Full article...)