Roosevelt Island is, along with Manhattan, part of New York County. The Roosevelt Island Development Corporation prepared Roosevelt Island for residential apartments in the 1970s and published Manhattan’s Other Island: A Progress Report, Summer 1974. (1974). “Manhattan’s Other Island: Roosevelt Island” was a story that was published in the New York (NY) Times magazine section on December 1, 1974. The “Manhattan’s Other Island” nickname has been only infrequently used since 1980.
Roosevelt Island has also been called the “Little Apple.”
Wikipedia: Roosevelt Island
Roosevelt Island is a narrow island in New York City’s East River. It lies between Manhattan Island to its west and the borough of Queens on Long Island to its east, and is part of the borough of Manhattan. Running from the equivalent of East 46th to 85th Streets on Manhattan Island, it is about 2 miles (3.2 km) long, with a maximum width of 800 feet (240 m), and a total area of 147 acres (0.59 km2). Together with Mill Rock, Roosevelt Island constitutes Manhattan’s Census Tract 238, which has a land area of 0.279 sq mi (0.72 km2), and had a population of 9,520 as of the 2000 United States Census. It had a population of 11,661 as of the 2010 United States Census.
OCLC WorldCat record
Manhattan’s other island : a progress report, Summer 1974.
Author: Roosevelt Island Development Corporation.
Publisher: New York : Roosevelt Island Development Corp., 
Edition/Format: Print book : State or province government publication : English
1 December 1974, New York (NY) Times, magazine, pg 32, col. 1:
Manhattan’s other island: Roosevelt Island:
A case study in how to build, cable cars and all, a new town for 20,000
By Anthony Bailey
New York (NY) Times
Cable Over River Strung for Tram To Roosevelt Is
By LESLIE MAITLAND ();
August 08, 1975
Section The Week In Review, Page 58, Column , words
“Duck soup.” That’s what a Swiss tramway expert had said when asked to evaluate the feasibility of providing transportation from Roosevelt Island now billed as “Manhattan’s Other Island” to a point on Second Avenue via aerial cable cars.
16 October 1978, New York magazine, “Roosevelt Island: Trouble in Paradise” by Rinker Buck, pg. 70, col. 1:
Gleaming panels of glass set in designer brick, together with the color- coordinated, “pollution-free” minibuses that ply the island, complete the mirage of an aesthetically pleasing, carefree existence on “Manhattan’s Other Island.”
Visiting Roosevelt Island today, Manhattan’s ‘other island’. It has the only commuter aerial tramway in North America.
1:15 PM - 8 Aug 2010
New York (NY) Times
New York Today: Toasting Our Tramway
By JONATHAN WOLFE MAY 17, 2016
Roosevelt Island, nicknamed Manhattan’s Other Island, became so flooded with visitors that the tramway imposed a passenger limit because of complaints.