This is 99% invisible. I'm Roman Mars.

Over the years, I guess about 20 people have written to us suggesting that we do a story about the mysterious giant concrete arrows that dot the US landscape from New York to San Francisco.

If you don't know, these are about 70 feet of what looks pretty much like sidewalk concrete

in the shape of an arrow pointing Berkeley west.

They date from the 1930s and they were part of the transcontinental

airway system that helped planes carrying mail find their way across the US

before the age of reliable radar and GPS.

When they were operational, they were painted bright yellow and were accompanied by a tower topped

with a bright rotating beacon.

Today the towers and paint are long gone, but many of the giant arrows remain, sometimes

with weeds poking through the cracks in the concrete. They're super cool and fun to find on Google

maps, but that's about They're super cool and fun to find on Google Maps.

But that's about it.

There's not too much more of a story there.

I'm glad I know it.

I'm pleased I got to tell you about it.

It's totally a 99% invisible story. And I'm honored when people learn about them and they think I need to send this to Roman

But ultimately the arrows are not something on which we can hang a whole episode

We come across these kinds of stories all the time.

Not just as suggestions from the audience, but in our own research there are tons of little

interesting would-be 99 p. I stories that get cut out of an episode or just don't warrant six weeks of production and 20 minutes of airtime for whatever reason, but we still kind of love them.

So as a little change of pace, we thought we of love them.

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