The editorial that says, "Yes, Virginia, there is a Santa Claus..." is the most reprinted editorial in the English language, and with good reason.
One of my favorite lines is:
Nobody can conceive or imagine all the wonders there are unseen and unseeable in the world.
A few years ago, the letter was appraised on Antiques Road Show. You can see that here:
It's one of those stories that resonates with us, because we can all put ourselves in the place of the eight-year-old or the editor.
Read more about it and see the original letter and editorial on Letters of Note.