The Slinky became a toy craze in 1945 and has sold millions of pieces. It all started in Philadelphia.

Philadelphia Navy Yard mechanical engineer Richard James was experimenting with a torsion spring in 1943 when the coil tumbled from his desk and landed on a stack of books.

The spring didn’t just sit there. The top coil flipped over onto the next book. Then the back coil flipped over to the next book. Before he knew it, this newfangled thing was taking the hardcovers like stairs.

Fascinated, James went home and showed the new toy to his wife, Betty.

She was enthralled and named the metal thingamajig a Slinky because of its wavy, stealthy movement.

James finagled with the metal spring for about two years, perfecting its flip-flop down-the-stack movement. Finally, on Nov. 27, 1945, the Jameses brought 400 Slinkies to Gimbels at Eighth and Market Streets, debuting them to shoppers. The whole lot sold out in 90 minutes for $1 a piece.

A toy craze was born.

This Saturday, the Philadelphia Historic District will host a “Firstival” to fete the Slinky at the American Philosophical Society from 11 a.m. to 1 p.m. The society’s archives house the 1953 study “On Slinky: The Dynamics of a Loose, Heavy Spring” by British mathematician and oceanographer Michael Longuest-Higgens.

Firstivals are weekly day parties celebrating America’s 250th birthday. This week’s Firstival is the 35th.

After the roaring success at Gimbels, Richard James quit his $50-a-week gig at the Navy Yard and founded James Industries, manufacturing Slinkies from a Germantown warehouse. Each Slinky was made from 80 feet of steel on a machine that James invented. It took 10 seconds to make each Slinky.

Slinkies, considered the first toy craze, predating Cabbage Patch Kids, Tickle Me Elmo, and Beanie Babies, were so popular in the 1940s that Macy’s stopped selling them for a bit because the swarming crowds created a fire hazard.

In the early 1950s, published reports said the Jameses were making more than $1 million a year. James denied those reports in a 1950 Inquirer article but admitted to making “solid profits.” By the end of the decade, the Jameses’ Slinky operation had moved to manufacturing facilities in Clifton Heights and Paoli.

The couple divorced in 1961.

Richard James became a missionary in Bolivia, leaving his wife to manage the business and their six children. Betty James moved her children closer to family in Hollidaysburg, Pa., and commuted to the Philadelphia area for three years before moving the company closer to home in 1964.

In 1962, Betty James launched an aggressive television campaign to build awareness and increase Slinky sales. Songwriters Homer Fesperman and Charles Weagley wrote the unforgettable, now-iconic Slinky jingle.

“It’s Slinky, it’s Slinky. For fun it’s a wonderful toy.

It’s Slinky, it’s Slinky. It’s fun for a girl or a boy.

It’s fun for a girl or boy!”

The Slinky dog became a party trick. People wore Slinky glasses. Plastic Slinkies were introduced to the market.

The Slinky was everywhere.

“During the Vietnam War, soldiers used Slinkies as portable radio antennas,” said Zach Delphais, the public relations manager for Just Play Products, the Bucks County-based brand that owns Slinky today.

Betty James sold Slinky to Michigan-based Poof Industries in 1999.

In 2001, Betty James, then 84, was inducted into the Toy Industry Hall of Fame. At that time, more than 250 million Slinkies had been manufactured from hundreds of thousands of tons of steel.

Betty James died in 2008 at age 90.

In 2020, Just Play acquired Slinky at auction.

Today, Just Play makes about 3 million metal Slinkies a year. They sell between $3 and $4 a piece.

“Slinky has lasted because it’s simple, it’s iconic, and every generation has connected with it,” Delphais said. “It started right here in Philadelphia. That makes it all the more meaningful.”

This week’s Firstival is Saturday, Aug. 29, from 11 a.m.-1 p.m., at the American Philosophical Society, 104 S. Fifth St.

Each week, The Inquirer is highlighting a “first” from the Philadelphia Historic District’s 52 Weeks of Firsts. A “52 Weeks of Firsts” podcast, produced by All That’s Good Productions, drops every Tuesday.