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The year is 1988.

A new commercial appears on TVs across the country.

Like most effective commercials, this one is simple and short.

It features Walter Stack, an 80-year-old union organizer.

He's famous in the San Francisco Bay area for running shirtless from Fisherman's Wharf to Saw Salito and back in full view of thousands of morning commuters.

The stack gleefully crosses the Golden Gate Bridge. The camera zooms in to capture the breath puffing from his mouth. His sneakers slapping the asphalt.

The ad draws to a close on a black screen and three words. Just do it.

Today, those words have become as synonymous with Nike as the signature swooosh.

But in 1988, the tagline was seen as something of a gamble, a big statement.

It had been developed by Dan Whedon, the co-founder of the ad firm Whedon in Kennedy.

The inspiration bizarrely enough were the final words of the infamous murderer Gary Gilmore.

In 1977, as the firing squad trained their guns on Gilmore, he called out to them. Let's do it.

Whedon, a savvy marketer, didn't love the context. But then again, viewers didn't have to know where he got the idea from, right?

All they had to do was respond to the words, which they did.

Soon, just do it is appearing on billboards and magazine and newspaper ads and in more TV commercials.

It becomes the mantra for people trying to push themselves to do something big, do something tough.

The most famous of these ads airs a couple of years later in 1990.

Unlike the Walt Stacks box, the new ad doesn't focus on just one athlete.

Instead, it's a whole parade of celebrities. Superstar is signed to Nike.

Michael Jordan, rising toward the rim. Wayne Gretzky, his blonde hair perfectly quaffed.

Bo Jackson jackhammering a pitch into the atmosphere. And Spike Lee, a filmmaker, adoringly holding up a Nike sneaker.

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