The construction of the Rockefeller Center complex in New York City was an urban renewal project, spearheaded by American financier John D. Rockefeller Jr. to help revitalize Midtown Manhattan. The center occupies 22 acres (8.9 ha) on one of Columbia University's former campuses, with some 17 million square feet (1.6×106 m2) of office space. All structures in the original complex were designed in the Art Deco style. Excavation of the site started in April 1931, and construction of the first buildings began that September. The first of the complex's edifices was opened in September 1932, and most of them were completed by 1935. The final three buildings in the original complex were built between 1936 and 1940. The project employed over 40,000 people and was the largest private construction project at the time. An additional building went up at 75 Rockefeller Plaza in 1947, and another at 600 Fifth Avenue was built in 1952. Four towers were built in the 1960s and 1970s. (Full article...)