Santa Claus is a myth told to children, but he does have historical roots in St. Nicholas. The legend of St. Nicholas dates back to 280 A.D. St. Nicholas was a monk who became the source of many stories, though the validity of the stories is unknown.
Legend claims that St. Nicholas traveled around giving away his inherited wealth to those who were sick or poor. There is also a popular story of him saving three unmarried sisters from slavery by supplying them with dowries in order to marry.
St. Nicholas' legend was brought to America by the Dutch, who celebrated his death and called him Sinter Klaas, a nickname that evolved into Santa Claus. Washington Irving also helped to popularize his legend through stories.
In the early 19th century, shopping malls and the Salvation Army began to propagate the image of Santa Claus that most people are familiar with today.