
McCay went off to a studio where he and an assistant drew the "10,000 drawings"
which were inspired by the dinosaur exhibits in the AMNH.
Up until the invention of computers, modern animation used sheets of celluoid called "cels." Since cels are transparent, you can see the background through them. They eliminate the work of re-drawing backgrounds. When McCay made Gertie, however, cels were not yet invented, and all of the backgrounds were drawn by hand.
A gag in the film had McCay's assistant drop all of the drawings onto the floor when McManus comes to visit the New York City animation studio.
McCay worked for nearly
2 years.