For New Yorkers, the lighting of the Rockefeller Center Christmas tree marks the start of the holiday season and is a tradition that brings our city together. It began in 1931, when workmen set up a tree in the middle of the construction site, and the management has installed a great tree every year since. In 1942, with the nation at war, three large Christmas trees were set up, one with red ornaments, another white, a third blue as a patriotic gesture. Rockefeller Center did not originate the idea of a great public Christmas tree, however.