"The district was created when dealers moved north from an earlier district near Canal Street and the Bowery that was created in the 1920s, and from a second district located in the Financial District, near the intersection of Fulton and Nassau Streets, which started in 1931. The move uptown started in 1941. The district grew in importance when the German Nazis invaded the Netherlands and Belgium, forcing thousands of Orthodox Jews in the diamond business to flee Antwerp and Amsterdam and settle in New York City. Most of them remained after World War II, and remain a dominant influence in the Diamond District...

It has been reported[2] that total receipts for the value of a single day's trade on the block average $400 million. There are 2,600 independent businesses located in the district, nearly all of them dealing in diamonds or jewelry. Most are located in booths at one of the 25 "exchanges" in the district. Many deals are finalized by a simple, traditional blessing (mazel und brucha[1]) and handshake. The Diamond Dealers Club — also known as the DDC — is an exclusive club that acts as a de facto diamond exchange and has its own synagogue. Retailers with shops line the streets outside. Above the bazaar is the Gemological Institute of America which trains gem dealers." Wikipedia