Following the murder of Siegel in Los Angeles in 1947, Greenspun renewed his interest in his Jewish heritage and became a prominent figure in supporting the struggle to establish the State of Israel.
On June 17, 1972, Virgilio González, Bernard Barker, James W. McCord, Jr., Eugenio Martínez and Frank Sturgis were arrested while placing electronic devices in the Democratic Party campaign offices in an apartment block called Watergate, in Washington, D.C.
It later emerged that people working for President Richard Nixon wanted to wiretap the conversations of Larry O'Brien, chairman of the Democratic National Committee.
McCord testified that Attorney General John N. Mitchell had told him that Greenspun had in his possession blackmail type information involving a Democratic candidate for president.
[citation needed] Immediately after Greenspun's death, his family entered the Sun into a joint operating agreement with the Las Vegas Review-Journal.
Greenspun was also heavily involved in real estate, acquiring most of the western portion of Henderson, Nevada for a development that eventually became Green Valley.
His family controls the majority of this land and associated real estate developments, including golf courses and the Green Valley Ranch, Resort and Spa with interest being held through The Greenspun Corporation.