The history of plastic injection molding begins in 1868 when inventor John W. Hyatt patented the process of creating celluloid, a material originally intended to replace the ivory used in billiard balls. In 1872, Hyatt and his brother Isaiah patented the first injection molding machine, which used a simple plunger mechanism to push celluloid through a heated cylinder and into a mold. The device led to the development of a booming manufacturing industry that produced buttons, combs, collar stays, and other items from celluloid.

Soluble forms of cellulose acetate became available in the early 1900s, offering a much less flammable substitute for previous materials. In the lead-up to World War II, many of the thermoplastics commonly used today — including polystyrene and polyvinyl chloride (PVC) — were developed.