Earliest known, along with one of the most recent known, photographs of a President

[Tanuki]

19. In the early days of portrait photography, people usually had a serious facial expression.

You could almost say that smiling was frowned upon.

https://www.washingtonpost.com/news/wonk/wp/2015/12/01/researchers-have-discovered-a-surprising-reason-we-smile-in-photos

"Smiling is a biological reflex. Babies practice smiling as soon as they are born, their bodies rehearsing this essential human gesture. 

But to smile for the camera, to mug and pose, is strictly a learned habit. Historians say that the photographic grin not only a recent ritual, but also a somewhat artificial one: abetted by the camera industry, and entwined with the rise of cheerfulness as an American cultural norm.
....
Though photography was still relatively new in the 1850s, portraiture was not, and tradition said that proper people should not grin or bare their teeth in their pictures. Big smiles were considered silly, childish, or downright wicked.

“In the fine arts a grin was only characteristic of peasants, drunkards, children, and halfwits, suggesting low class or some other deficiency,” Kotchemidova writes, citing research from historian Fred Schroeder."...(moreĺ