Most of the existing buildings were demolished starting in the 1930s, when the Triborough (now Robert F. Kennedy) Bridge, two parks, and a wastewater treatment plant were developed there.

Most of Randalls and Wards Island is parkland with athletic fields, a driving range, greenways, playgrounds, picnic grounds, and the Icahn Stadium track-and-field facility.

[7] Surrounding Randalls Island was a narrow strip of marshland, and there were larger marshes to the north and southeast, which drained into the East River.

[18] The Sunken Meadow section of Randalls Island Park comprises 85 acres (34 ha) and contains ball fields.

[27] The Lenape, a Native American people indigenous to New York City, called Wards Island Tekenas[28][15] or Tenkenas.

[36] At the time of European contact in the early 17th century, there were 900 Wecquaesgeek Lenape living in what is now Upper Manhattan, the Bronx, and lower Westchester County.

[41] Wouter Van Twiller, the Director General of New Netherland, obtained the island from two Lenape chiefs named Numers and Seyseys[13][28] on July 16, 1637.

[33] The New York Times describes an "amiable English gentlemen of quiet tastes", George Talbot, as being the next occupant of Pipon's house.

His brother Bartholomew bought the remainder of Great Barn Island from John Molenaar, who in turn had acquired that land from Pinfold.

[65][66] The two-story State Emigrant Hospital and the three-story Refuge for Destitute Immigrants on Wards Island both opened in July 1866;[65][67] its design was based on a plan by the social reformer Florence Nightingale.

[101][106] Other bodies were relocated from the Madison Square and Bryant Park graveyards,[107] and immigrants who died at the State Emigrant Hospital were also interred there.

[154] City government architect Raymond F. Almirall filed plans for a four-story nurses' home on Randalls Island the next year;[155] that building opened in 1912.

[179] That April, in anticipation of the Triborough Bridge's completion, city parks commissioner Robert Moses announced that he would convert 140 acres (57 ha) on Randalls Island to parkland.

[190] The Works Progress Administration began developing the southern end of Wards Island that year, demolishing what was left of the Homeopathic Hospital.

[195] Wards Island Park was delayed during the 1940s,[196] and Manhattan State Hospital remained open past 1943, despite having been ordered to shut down.

[76] The city government announced in 1955 that it planned to connect Randalls and Wards Islands by allowing private contractors to dump debris within Little Hell Gate for free.

[209] The Triborough Bridge and Tunnel Authority announced in 1962 that it would allow contractors to fill the eastern portion of Little Hell Gate and the northern corner of Randalls Island.

[240] In addition, part of the Charles H. Gay Shelter was converted to a women's jail in 1989 to accommodate the increasing number of inmates in the city.

[242] The park was used by dozens of local schools at the time and had various baseball, rugby, tennis, softball, soccer, lacrosse, and cricket fields.

[250][252] In addition, there were fears that the presence of the Charles H. Gay Center and the Wards Island Bridge were contributing to increased crime in neighboring East Harlem.

[259] The plan entailed demolishing Downing Stadium; adding an amphitheater and new athletic facilities, restoring wetlands; building trails, marinas, restaurants, and ferry stops; and constructing a water park.

[265] In April 2006, the first section of a waterfront pathway opened on Randalls Island, and officials began restoring the Little Hell Gate wetlands.

[269][270] In 2007, twenty private schools agreed to pay the city government $52.4 million, in exchange for the exclusive use of two-thirds of the island's fields during weekday afternoons.

[268] Randalls Island Park contains over 8 miles (13 km) of pedestrian and bike pathways[292] and connects with Manhattan, the Bronx, and Queens.

Through the process of excavating over 20,000 cubic yards (15,000 m3) of debris, installing clean sand, and planting native marsh grasses, 4 acres (1.6 ha) of saltmarsh has been created surrounding the Little Hell Gate Inlet on the western edge of Randalls and Wards Island.

[299] After the removal of almost 15,000 cubic yards (11,000 m3) of debris and fill, the freshwater wetland site was planted with native herbaceous, shrub, and tree species, such as switchgrass, aster, dogwood, and oak.

[278] In August 2023, a migrant shelter for 3,000 people opened at Randalls Island after the number of asylum seekers traveling to the city increased sharply.

[319] The plant originally occupied 77 acres (31 ha) on Wards Island's northeast corner[200] and could treat up to 180 million U.S. gallons (680×10^6 L)[f] of raw sewage daily when it opened in 1937.

[330] The Triborough Bridge opened on July 11, 1936, providing a direct road connection from the then-separate islands to the rest of the city.

[338] Designed by Othmar Hermann Ammann and built by the U.S. Army Corps of Engineers,[339] the footbridge was originally known as the Harlem River Pedestrian Bridge.