It was the first war that was photographed

 From War photography - Wikipedia The Mexican-American War was the first one to be captured by a camera.^[1] A number of daguerreotypes were taken of the occupation of Saltillo during the Mexican–American War, in 1847 by an unknown photographer, although not for the purpose of journalism.^[2][3] The photographs do not show the wounded, dead bodies, nor live combat zones, with no glorification of warfare being evident.^[1] What they do show are portraits of military men, landscapes, street scenes, and post-battle burial grounds.^[1]

Lieutenant George Henry Gordon during the Mexican-American War (1846-1848). 

Mexican-American War daguerreotype image showing American General Wool and staff in the Calle Real, Saltillo, Mexico, c. 1847.

(Amon Carter Museum of American Art).

American soldiers standing along a street in Saltillo, Mexico, during the Mexican-American War, c. 1847.