According to the St. Nicholas Center, the persona of Santa Claus is loosely based on St. Nicholas, a bishop in Myra, Turkey who became the patron saint of children. Primarily through Dutch settlers celebrating his feast day, St. Nicholas became known as "Santa Claus" over time.
The Dutch settlers in America who celebrated St. Nicholas's feast day referred to him in Dutch as "Sinter Klaas." Their celebrations gradually were incorporated into other American Christmastime festivities in the 18th and 19th centuries. The transition to the Santa Claus image popular today was hastened by the 1823 publication of Clement Moore's poem "A Visit from St. Nicholas," more popularly known as "'Twas the Night Before Christmas." In addition, images by 19th century cartoonist Thomas Nast, Norman Rockwell and Coca-Cola advertisements from the 1940s cemented the popular idea of what Santa Claus looks like.