Rockefeller Center Christmas Tree Lighting Ceremony - November 28, 2012 from 7-9 p.m. - On NBC Television
While not officially a National Christmas Tree, New York City's Rockefeller Center Christmas Tree is the biggest, brightest, most famous Christmas tree on our planet. It's lighting is an annual television event. The tree is nearly always a Norway Spruce and grown by enthusiasts hoping for the honor of having their tree chosen to be displayed at Rockefeller Center. The event takes place just after the Thanksgiving holiday weekend.
There is - or are - several official national trees. I am still not certain as to which is the most official, but there are at least four trees that can make that claim: National Christmas Trees - All the Confusion

Comments
I live in the panhandle of Florida and looking for a 15-20 foot high, non deciduous, fast growing privacy tree or hedge without berries, blossoms or thorns. I have thought about leyland cypress but I wonder if it’s too much work. Any ideas or suggestions.
Mike,
A Leyland Cypress gets much taller than 15-20 feet, and they do not prune well. They typically get to over 30 feet, and taller. They are also prone to bagworms. They grow very fast, and die young. I suggest contacting your Forestry service Agent for a native plant that does well in your area. If you can not get in touch with an agent, call the nearest university with a Forestry School, and ask for a Forestry Professor. I am sure many people would appreciate your writing back in with the best plant suggested.
Scotty