Probably best known for his 1914 landmark, rice-paper drawn animation Gertie the Dinosaur, Winsor McCay displayed his first use of animation drawn on celluloid (as in "animation cels") with The Sinking of the Lusitania. In 1918, Lusitania was the longest running animation to date.
What is particularly interesting here is the attempt at a dramatic "animated documentary" form. Though we might initially think of this as an antiquated or even failed form of documentary storytelling, there are a number of significant modern documentaries that use animation as a key element of capturing and shaping history, as with Bret Morgen's Chicago 10 (2007) and Ari Folman's Waltz With Bashir (2008).