The Man Who Perfected the Modern Zipper: The Decades-Long Patent Battle Behind the World’s Most Satisfying Fastener

I went looking for the history of the zipper because I was curious who invented it, and I came out the other side with a story involving a grief-stricken Swedish engineer who buried himself in work after his wife died, an inventor whose main product kept spontaneously falling open, a rubber company that named the whole thing, and a 60-year gap between the first patent and the first working fastener.

That gap is the part that gets me. Elias Howe, who also invented the sewing machine, patented something called the “Automatic, Continuous Clothing Closure” in 1851. He then completely abandoned the idea and never built a working version. The zipper sat in a patent file, unbuilt, for over forty years until someone else started working on it independently.

Whitcomb Judson and the Clasp Locker

The next person to take a serious run at the problem was Whitcomb Judson, a Chicago engineer who reportedly got the idea while struggling to lace his own boots. In 1893 he debuted his invention, which he called the Clasp Locker, at the Chicago World’s Fair.

The Clasp Locker was a row of hooks and eyes connected by a slide mechanism. The concept was basically right. The execution had one significant problem: it kept opening by itself. The hooks would pop apart under pressure. Boots would unlace themselves mid-walk. Bags would unclip without warning. Judson knew the device needed improvement, so he founded the Universal Fastener Company with a business partner, Colonel Lewis Walker, to manufacture and refine it. He hired an engineer to fix it. The engineer’s name was Gideon Sundback.

Gideon Sundback and the Problem He Could Not Leave Alone

Sundback was born in Sweden in 1880 and trained as an electrical engineer in Germany before emigrating to the United States in 1905. He joined the Universal Fastener Company and quickly rose through the organization, partly through skill and partly because he married the plant manager’s daughter, Elvira Aronson. By 1909 he was the head designer.

In 1911, Elvira died. She was 29 years old. The couple had one daughter together. Sundback was devastated. He threw himself into his work with the intensity of someone who needed the distraction badly.

Between 1911 and 1913, he redesigned the fastener entirely. Judson’s original device had four fastening elements per inch. Sundback increased this to ten. He replaced the hooks and eyes with small interlocking teeth. He designed two facing rows of teeth that a slider pulled together in a single smooth motion. He figured out the geometry that made the teeth lock securely and also release cleanly, which sounds simple and apparently required years of failed iterations to achieve.

On April 29, 1913, Sundback filed for patent protection for what he called the Hookless Fastener No. 1. That date is now celebrated as National Zipper Day, which is a thing that exists. In 1917, the US Patent Office issued patent number 1,219,881 for the Separable Fastener, the design that became the functional template for every zipper made since.

The Manufacturing Problem He Also Solved

Inventing a better fastener was only part of the challenge. Producing it at any scale was another problem entirely. Sundback also designed the machine that made the teeth. He called it the S-L machine. It took a Y-shaped wire, cut small scoops from it, and punched dimples into each piece to create interlocking teeth. The machine stamped out teeth continuously and assembled them onto a tape at a rate that made commercial production feasible. Without the manufacturing solution, the design patent would have remained a drawing.

By 1917, Sundback had given the world both a zipper that worked reliably and a method to produce thousands of them a day. The Universal Fastener Company started selling them to manufacturers of money belts and boots for the US military during World War I. Clothing was not yet the primary application.

Who Named It and Why

The word zipper did not exist until 1923. That is when the B.F. Goodrich Company, the rubber manufacturer, started using Sundback’s Separable Fastener on a new line of rubber boots. Goodrich executives loved the sound the fastener made when you ran the slider up the teeth. They called the boots Zipper Boots. The name stuck to the product and then transferred to the mechanism itself. Sundback’s invention had been commercially available for six years before anyone named it.

B.F. Goodrich trademarked “zipper” initially. The trademark lapsed, the name passed into common usage, and nobody now thinks of rubber boots when they hear it. This is one of the more successful accidental rebranding events in consumer goods history.