Well, of course you know who wrote what is commonly known as "The Night Before Christmas"! It was Clement C. Moore. After all, it's on all the books!
But was it? Descendants of Henry Livingston Jr., who frequently wrote verse in the meter of the "visit," claim it was Livingston who wrote the poem. They cite the fact that Moore was a humorless theologian, and that he did not claim the poem as his until years later.
Some links about the controversy:
All About "A Visit from St. Nicholas" - Collaborative Essays and Articles
Who Wrote "'Twas the Night Before Christmas'?"
A Recent Poughkeepsie Journal Article About the Debate
Boston Globe Article About New Publication of the Story
The Claims for Henry Livingston Jr as the Author
The Authorship of The Night Before Christmas