On a recent rainy weekend, my family and I bought our Christmas Tree. We got it tied to the roof, drove it home, set-up in the stand, and watered it. Now it's time for the lights. So I tested them. And two strands worked. Sigh. Off to Target.
Standing in front of a wall 20 feet long of Christmas lights was daunting, do I want white lights or color? I decided on white. Oh, well then do you want warm white, cool white, bright white, classic white? And then do you want LED or Incandescent? What bulb shape? How many? And should I get energy efficient. My electrical designer's brain was looking at the color temperatures and wattages and becoming overwhelmed. Finally, I just picked the ones on sale. Easy peasy.
This experience made me wonder how something the idea Christmas lights were even started. Why do we put lights on the trees in our house? There must be an engineer behind this idea somewhere.
According to Jamie Malanowski in an article for the Smithsonian Magazine, "Untangling the History of Christmas Lights," it was indeed an engineer behind the idea. Edward Hibberd Johnson was an investor in Thomas Edison's work and later served as the chief engineer of his West Orange Laboratory. In 1884 however, he was the Vice-President of the Edison Electrical Light Company. And according to the Smithsonian article, "Johnson saw an opportunity. Setting up a tree by the street-side window of his parlor, Johnson hand-wired 80 red, white and blue light bulbs and strung them together around it, and placed the trunk on a revolving pedestal, all powered by a generator."
The New York Times wrote an article on December 27th, 1884 reporting on the event:
IN AND ABOUT THE CITY
A BRILLIANT CHRISTMAS TREE
HOW AN ELECTRICIAN AMUSED HIS CHILDREN.
"A pretty, as well as novel Christmas tree, was shown to a few friends by Mr. E. H. Johnson, President of the Edison Company for Electric Lighting, last evening in his residence, No. 139 East Thirty-sixth-street. The tree was lighted by electricity, and children never beheld a brighter tree or one more highly colored than the children of Mr. Johnson when the current was turned and the tree began to revolve. Mr. Johnson has been experimenting with house lighting by electricity for some time past, and he determined that his children should have a novel Christmas tree.
It stood about six feet high, in an upper room, last evening, and dazzled persons entering the room. There were 120 lights on the tree, with globes of different colors, while the light tinsel work and usual adornment of Christmas trees appeared to their best advantage in illuminating the tree. Mr. Johnson had placed a little Edison dynamo at the foot of the tree, which, bypassing a current through from the large dynamo in the cellar of the house, converted it into a motor. By means of this motor, the tree was made to revolve with a steady, regular motion. The lights were divided into six sets, one set of which was lighted at a time in front as the tree went round. By a simple device of breaking and making connections through copper bands around the tree with corresponding buttons, the sets of lights were turned out and on at regular intervals as the tree turned around. The first combination was of pure white light, then, as the revolving tree severed the connection of the current that supplied it and made connection with a second set, red and white lights appeared. Then came yellow and white and other colors. Even combinations of the colors were made. By dividing the current from the large dynamo, Mr. Johnson could stop the motion of the tree without putting out the lights." 
Those bulbs were expensive, and electricity wasn't widely available. So the idea was way ahead of its time. According to Malanowski, one string of 16 lights was the equivalent of $350 today. They required generators and electrician wiring.
Thirty years later, the White House had its first electric lit tree with President Grover Cleveland in office, and the idea became more mainstream. Soon everyone had lights on their trees.
So when you are gathered around the tree Christmas morning, and catching the perfect pictures with those flickering lights, whether they are multi-color, warm white, bright light or red, just remember an engineer helped to make this moment possible.
Read more on the history of the Christmas Tree Lights:
National Electrical Contractor's Association: A Few Facts About The Origin Of Electric Christmas Lights
Smithsonian Magazine, Untangling the History of Christmas Lights