When Germany annexed Austria in 1938, he emigrated to the United States. Short and stout, he landed "with an architect's degree, eight dollars, and no English." Arriving in New York he changed his name to "Gruen" from Grünbaum and started to work as a draftsman. After the success of his design for the Lederer leather-goods boutique on Fifth Avenue, he received further commissions for the design of shops, including Ciro’s on Fifth Avenue, Steckler’s on Broadway, Paris Decorators on the Bronx Concourse, and eleven branches of the clothing chain Grayson’s.