David Rockefeller his graduate studies, he received a Ph.D. from the University of Chicago in 1940. After completing his studies in Chicago, he became secretary to New York Mayor Fiorello La Guardia for eighteen months in a "dollar a year" public service position. Although the mayor pointed out to the press that Rockefeller was only one of 60 interns in the city government, his working space was, in fact, the vacant office of the deputy mayor. From 1941 to 1942, Rockefeller was assistant regional director of the United States Office of Defense, Health and Welfare Services. Rockefeller enlisted in the U.S. Army
Rockefeller Center assistant, Lucienne Bloch.) Rivera's fresco in the Center was replaced with a larger mural by the Catalan artist Josep Maria Sert, titled "American Progress", depicting a vast allegorical scene of men constructing modern America. Containing figures of Abraham Lincoln, Mahatma Gandhi, and Ralph Waldo Emerson, it wraps around the west wall of 30 Rockefeller Plaza's Grand Lobby. In its earliest years, Rockefeller Center received largely negative and pessimistic reviews from architectural critics. The most cynical opinion came from renowned architectural scholar Lewis Mumford, who so hated the "weakly conceived, reckless, romantic chaos" of the March 1931 plans for Rockefeller Center