The institute was named for the Spanish city of Manresa, in which Saint Ignatius of Loyola, the founder of the Society of Jesus, wrote his Spiritual Exercises.

In 1860, he spent thousands of dollars to build a causeway across the marsh to connect it to the mainland,[3] allowing carriages to cross from South Norwalk.

[5] With growing interest in religious retreats for laymen around the turn of the 19th century,[6] the provincial superior of the Maryland-New York Province of the Society of Jesus, Joseph Hanselman, charged Fr.

[12] The Jesuits formally inaugurated the Manresa Institute on Keyser Island on April 21, 1889 (Easter Sunday), as the only facility in the United States dedicated solely to hosting retreats.

[4] The institute was named after the Spanish city of Manresa, where Saint Ignatius of Loyola, the 16th-century founder of the Society of Jesus, wrote the Spiritual Exercises.

[4] In 1911, Shealy decided to move the Manresa Institute to Staten Island in New York City,[13] where he purchased the Fox Hill Villa near Fort Wadsworth.

[17] A major spill of fuel oil occurred in 1969, causing significant ecological damage to the beach at Village Creek and the surrounding tidal flats.

In response to the Resource Conservation and Recovery Act, the first official recognition of the ecological damage done to the surrounding area by the plant was made in 1980.

[19] The southern parcel, which contains the original, much smaller island, houses the decommissioned power plant and support infrastructure, as well as an electrical substation.

The study was completed in 2019 and recommended four potential options for redevelopment of the southern parcel of the land: a marina, a solar farm, an educational facility, or a residential development.

[22] The Connecticut Department of Transportation announced in 2020 that it was considering using Manresa Island as a construction staging area for the project to replace the Norwalk River Railroad Bridge.

[23] The undeveloped portion of Manresa Island, which consists of a coastal forest as well as intertidal estuaries, is one of the last remaining undisturbed marine habitats on the Fairfield County coast.