According to the book 'One Night Stands with American History,' 17th century Dutch settlers brought the jolly fat man to America's shores and their image of Santa was “tall, slender and very dignified” without his trademark beard. (He was based on the traditional Dutch winter figure Sinterklaas.) Artist and political cartoonist Thomas Nast added the beard and the rotund figure in the pages of 'Harper's Weekly' during the latter part of the 19th century.
Santa got fat in America? Figures.