Before sea walls and other structures were built on the island, the exposed rock varied in size from about one acre to 175 square feet depending on the tide.

As a result of engineering surveys designating the area around New Rochelle and Port Washington on Long Island Sound as the ideal locality for a radio transmitter to serve the metropolitan New York area, new stations were constructed on these sites by both the Columbia ("CBS") and National ("NBC") broadcasting systems in 1940.

[1] [2] CBS spent approximately $500,000 to construct the transmitter building with emergency housing for ten workers, and the 410-foot (125 m) broadcast tower.

CBS's work to build a high-power broadcasting station included drilling through bedrock to a source of fresh water, found at a depth of 910 feet (280 m).

[2] The island was then purchased by the show-business couple Peter Lind Hayes and Mary Healy, who broadcast a breakfast conversation show from their home there.