Nast's first depiction of Santa Claus for Harper's Weekly, January 3, 1863

The political cartoonist Thomas Nast created the first depiction of Santa Claus as a bearded, sleigh-riding resident of the North Pole.
The cartoons were a bit of political propaganda, meant to associate the familial warmth of Jolly Old St. Nick with the Union cause.

"Santa's Portrait," by Thomas Nast (1881)

Nast's Santa Claus cartoons were so popular that Harper's Weekly continued to publish them every year until 1886.  His portrayal of Santa Claus as a rosy-cheeked, white-bearded fellow has remained in the popular consciousness to this day.

"The Promised Land,'as seen from the Dome of St. Peter's, Rome," by Thomas Nast (1870)

Nast had strong political convictions, chief among them a contempt for the Democratic party, the corruption of the Tammany Hall political machine in New York and the Irish-Catholics he associated with it. This cartoon shows the pope and Catholic clergy standing on top of St. Peter's, greedily eyeing the United States through a telescope.

"A Roman Catholic Mission from England to the 'heathens' of America," Thomas Nast (1871)

This cartoon shows an English cardinal ready to shackle emancipated slaves in America.

"The American River Ganges. The priests and the children," by Thomas Nast (1871)

The cartoon depicts Catholic bishops as crocodiles ready to devour American schoolchildren.

"Tied to His Mother's Apron-Strings," by Thomas Nast (1872)

Uncle Sam is shown offering to free a Catholic priest from the control of the pope.

"Wolf at the Door, Gaunt and Hungry," by Thomas Nast (1876)

These children are holding the door of the "Public-School System" against a wolf who is trying to break in. The wolf's collar is labeled "Democrats" and the tag is labeled "The Foreign Roman Church."

"Madness (Yet there's method in it)," by Thomas Nast (1876)

This cartoon shows the United States preventing Catholic nuns from entering a school as a teacher.