Well, to make a long story short, Ed Koch was Jewish!
Since Ed Koch's mother was Jewish, and in Orthodox Judaism and Conservative Judaism, those with a Jewish mother (or those who underwent a halakhic conversion) are considered Jewish, then that makes him Jewish. His father was Jewish too.
Ed Koch (whose full birth name was Edward Irving Koch) was born on December 12, 1924 in The Bronx, New York, U.S.. Ed Koch passed away on February 1, 2013 (aged 88).
He served in the United States House of Representatives from 1969 to 1977 and three terms as mayor of New York City, which he led from fiscal insolvency to economic boom from 1978 to 1989.
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