stylistic:tone
20th century

L. Frank Baum 's The Life and Adventures of Santa Claus, a children's book, was published in 1902. Much of Santa Claus's mythos was not firmly established at the time, leaving Baum to give his "Neclaus" (Necile's Little One) a variety of immortal support, a home in the Laughing Valley of Hohaho, and ten reindeer—who could not fly, but leapt in enormous, flight-like bounds. Claus's immortality was earned, much like his title ("Santa"), decided by a vote of those naturally immortal. This work also established Claus's motives: a happy childhood among immortals. When Ak, Master Woodsman of the World, exposes him to the misery and poverty of children in the outside world, Santa strives to find a way to bring joy into the lives of all children, and eventually invents toys as a principal means. Santa later appears in The Road to Oz as an honored guest at Ozma's birthday party, stated to be famous and beloved enough for everyone to bow even before he is announced as "The most Mighty and Loyal Friend of Children, His Supreme Highness – Santa Claus".

Images of Santa Claus were conveyed through Haddon Sundblom 's depiction of him for The Coca-Cola Company 's Christmas advertising in the 1930s. The image spawned urban legends that Santa Claus was invented by The Coca-Cola Company or that Santa wears red and white because they are the colours used to promote the Coca-Cola brand. Coca-Cola's competitor Pepsi-Cola used similar Santa Claus paintings in its advertisements in the 1940s and 1950s. Historically, Coca-Cola was not the first soft drink company to utilize the modern image of Santa Claus in its advertising— White Rock Beverages had used a Santa figure in monochrome advertisements for mineral water in 1915, and in 1923–25, the same company used colour images of Santa Claus in adverts for drink mixers. Earlier, Santa Claus had appeared dressed in red and white and essentially in his current form on several covers of Puck magazine in the first few years of the 20th century.

The image of Santa Claus as a benevolent character became reinforced with its association with charity and philanthropy, particularly by organizations such as the Salvation Army. Volunteers dressed as Santa Claus typically became part of fundraising drives to aid needy families at Christmas time.

In 1937, Charles W. Howard, who played Santa Claus in department stores and parades, established the Charles W. Howard Santa School, the oldest continuously run such school in the world.

In some images from the early 20th century, Santa was depicted as personally making his toys by hand in a small workshop like a craftsman. Eventually, the idea emerged that he had numerous elves responsible for making the toys, but the toys were still handmade by each individual elf working in the traditional manner.

The 1956 popular song by George Melachrino, "Mrs. Santa Claus", and the 1963 children's book How Mrs. Santa Claus Saved Christmas, by Phyllis McGinley, helped standardize and establish the character and role of Mrs. Claus in the US.

Seabury Quinn 's 1948 novel Roads draws from historical legends to tell the story of Santa and the origins of Christmas. Other modern additions to the "story" of Santa include Rudolph the Red-Nosed Reindeer, the 9th and lead reindeer created in 1939 by Robert L. May, a Montgomery Ward copywriter, andimmortalized in a 1949 song by Gene Autry.