The Slinky Was Not Intended to Be a Toy!
In 1943, Richard James wanted to develop a spring that kept fragile equipment steady on ships. He ended up knocking the spring to the floor and was shocked to see what happened. The spring "slinky walked" across the floor.
James quickly went home and shared the news with his wife. His wife Betty thought it would make a great toy. They presented it to the Gimbels Department Store in Philadelphia in 1945. In no time, it was the most popular toy of the year.
James used a machine that could compact 80 feet of wire into 2 inches. 

Source posted by Julia