It's an Olympic tradition: As teams from around the world parade in a grand opening ceremony, they briefly lower their flags in a show of respect as they pass the host nation's officials.

But at the Rio 2016 opening ceremony, you'll notice that Team USA won't lower their flag.

Indeed, the United States has a long tradition of ignoring this gesture.

Legend says it all started in 1908, when flag bearer Ralph Rose, an Irish American shot putter, refused to dip the US flag at the London Olympics.

"The suspicion is that because the Irish team then had to compete under the Union Jack, he refused to dip the flag to the Union Jack and to British officials, in protest," says Edgar B. Herwick III, who runs the Curiosity Desk at WGBH.

For a while after that, US flag protocol at the Olympics was a hodgepodge.

"We dipped it in Sweden in 1912. We didn’t dip in Belgium in 1920. We dipped again in Paris in 1924," says Herwick.

It became a solid tradition for the United States to not dip the flag in 1936. Then, both the Summer and Winter Olympics were in Germany. Hitler’s Germany.

"It was decided by the US [Olympic Committee] that year that our policy was we were not going to dip the flag. In fact we thought about not going to those Olympics, but what we settled on was that we're not going to dip the flag," says Herwick.

In the 1940s it became law. The Unites States adopted a federal flag code that makes it illegal to dip the US flag to "any person or thing."

Typical American exceptionalism, you might say. But nope, not this time.

The United States isn't the only country that has refused to lower their flag.

"Once the Soviet Union entered the Olympic movement in the 1950s, they stopped dipping their flag," says Herwick.

That started a sort of "flag arms race," according to Herwick.

"It got to the point where in 1992 [at the Olympics] in Albertville ... 60 of the 64 countries did not dip the flag."

Now, most countries are back to making the gesture.

The United States is still holding out.