September 1929: A month before the Wall Street Crash of 1929 and the beginning of the Great Depression, Columbia University signs a lease of 17 acres of Midtown space to the Rockefeller family. The money Columbia receives from the Rockefellers as rent amounts to 40 percent of Columbia's operating income.
1931: While Rockefeller Center is still under construction, workers put up a Christmas tree for the first time.
1933: The first official Rockefeller Center Christmas Tree Lighting Ceremony takes place. The 50-foot tree has 700 lights, and the ceremony is broadcast on NBC Red Network, the news giant's first radio network. This same year, the Top of the Rock is built. The land lease from Columbia is renegotiated, now lengthened to 1962.
1936: Rockefeller Center is illuminated by two trees, both 70 feet tall. The plaza's skating rink holds its first skating pageant during the Lighting Ceremony.
1942: In the midst of World War II, the ceremony celebrates the lighting of three trees. Each is decorated in a color of the American flag as a salute to overseas troops.
1951: The Kate Smith Show airs the Tree Lighting Ceremony for the first time as a national TV broadcast on NBC. Meanwhile, Columbia faces neighborhood opposition to expansion in Morningside Heights and Manhattanville.
1963: The 60-foot tree is on display for just three weeks before being taken down. Its wood is turned into mulch and donated to a Boy Scout troop. The mayor tells Columbia that the city will no longer assist the university in condemning Morningside buildings.
1966: The ceremony hosts its first foreign tree. Meant to celebrate Canada's Centennial in 1967, this tree is brought in from the greatest distance in the event's history.
1985: Columbia sells the land under Rockefeller Center, a total of 11.7 acres, for $400 million.
1999: The 1999 ceremony's tree, 100 feet high and just as many years old, is the largest in its history. The Norway Spruce, weighing over 20,000 pounds, hails from Killingworth, Connecticut.
2004: Swarovski designs a tree-topping star especially for the Tree Lighting Ceremony. The star, weighing in at 550 pounds, is embellished with 25,000 crystals.
2007: The 2007 ceremony's tree begins a legacy of eco-friendly practices. Thirty thousand LED lights adorn the tree with a fraction of the typical amount of electricity used. Rockefeller Center, in partnership with Habitat for Humanity, donates the tree at the end of the season to make lumber for future homes.