A naval engineer tried to make a ship stabiliser — the Slinky walked off his shelf

In 1943, naval mechanical engineer Richard James was working at the William Cramp and Sons shipyard in Philadelphia, developing springs to stabilise sensitive ship instruments at sea. He accidentally knocked a spring off a shelf and watched it 'step' down a stack of books, then across his desk. He told his wife Betty, 'I think if I got the right property of steel and the right tension, I could make it walk.'

James spent a year experimenting with different steel gauges and tensions until he found a spring that would consistently 'walk' down a surface. He and Betty borrowed $500, formed James Industries, and produced 400 units. On November 27, 1945, the Tuesday after Thanksgiving, they demonstrated the Slinky at Gimbels department store in Philadelphia using an inclined plane. All 400 sold out in 90 minutes at $1 each.

In 1960, Richard James told Betty he was leaving to become an evangelical missionary in Bolivia with Wycliffe Bible Translators. He relocated, leaving Betty with six children and the company. Betty divorced him, took over James Industries, and moved the factory to Hollidaysburg, Pennsylvania in 1964. She served as president from 1960 to 1998.

Under Betty's leadership, the Slinky became one of the most iconic toys of the 20th century. It was inducted into the National Toy Hall of Fame in 2000. The Slinky has been used in physics classrooms to demonstrate wave motion, in NASA zero-gravity experiments, and in military communications. Over 300 million Slinkys have been sold worldwide.