Short answers, pulled from the story.
The first documented American animation appeared on the 1st of January 1906 when the Vitagraph Company released Humorous Phases of Funny Faces. This short film featured crude stick figures performing magic tricks and interacting with a live-action audience. It proved that moving images could be drawn rather than filmed.
Walt Disney released Steamboat Willie on the 18th of November 1928. This film introduced Mickey Mouse to the world and marked the end of the silent era. It ushered in the Golden Age of American animation by synchronizing sound with animation.
The United States Army began collaborating with Walt Disney at his studio on the 8th of December 1941. This partnership led to the creation of training materials for troops and propaganda for the public. The animation industry was mobilized to support the war effort following the attack on Pearl Harbor on the 7th of December 1941.
Hanna-Barbera became a dominant force in American animation during the late 1950s television era. They produced popular shows like Scooby-Doo, Josie and the Pussycats, and Captain Caveman. These shows were designed to be cost-effective with fewer frames per second and simpler character designs.
Pixar debuted with the extremely successful Toy Story in 1995. This film was the first feature film to entirely use computer-generated imagery. It marked a technological revolution that demonstrated the potential of 3D computer animation.