Our image of Santa Claus comes primarily from the interpretations of illustrators over time. Here are a few examples.
Despite the fact hat Nast had given Santa his physical form and Reginald Marsh dressed him in the red suit with white cuffs, I think it’s J.C. Leyendecker to whom we owe our most complete contemporary image of His Jollyness.
(Images above, in chronological order: Thomas Nast [with detail], Reginald Marsh, Arthur Rackham, J.C. Leyendecker, N.C. Wyeth, Norman Rockwell and Haddon “Sunny” Sundblom)