The first experiments were of course the famous "Monkeyshines" films, three movies where the camera captures (or tries to capture) the images of Edison's workers as they move in front of it. While not exactly successful (image looks pretty bad), those movies were the very first films shot in America and showed Edison the enormous potential of Dickson's invention. After many experiments, Dickson achieved the quality he desired and made the movie that would be shown to the press and 150 members of the National Federation of Women's Clubs in a private demonstration of the invention that took place on May 20, 1891. The first movie shown was this one, nowadays aptly titled "Dickson Greeting" because it consisted of a short 3 seconds scene where William K.L. Dickson appeared bowing and smiling, as if he was indeed greeting the first audience of his Kinetoscope. There were rumours that this film was also the very first movie with sound, with Dickson saluting his employer as he greeted him, but those rumours were probably created by Edison to increase the attention (not the first time he would use this tactic), and because Dickson was really working in making "talkies" (and he would be close to really make it, I must say).
Watching how Dickson's work improved from the "Monkeyshines" experiments to this movie is an amazing experience, as the quality of his movies improved drastically from bizarre images without any shape that appeared in his first three films to the high quality of his image moving gracefully in "Dickson Greeting". The fact that all this improvements took him less than a year is certainly a testament of the enormous genius of this man, who singlehandedly put Edison's company on the race towards motion pictures. On that day of May, this along with two other Kinetoscope movies (probably the two shorts about boxing) were shown to an audience for the first time, in what would mark the birth of the first device invented to watch movies. Kinetoscope, cinema's "granddaddy" had just been born.
Buy "Dickson Greeting" (1981) and the rest of Edison's early films