How Toyota's 5 Whys Framework Saved the Lincoln Memorial

In the 1980s, the Lincoln Memorial was crumbling faster than expected. Marble was flaking off the structure, and the cause wasn’t time or weather, but something far more mundane: excessive cleaning. Every morning, maintenance crews were pressure-washing the monument with powerful chemicals to remove bird droppings, which were accumulating in absurd quantities. In an effort to stop the mess at its source, they installed bird nets. It worked, to a point, but made the monument look like an unfinished warehouse. Tourists complained. Photographs looked terrible. The nets were taken down.

Someone then asked what the birds were gathering at the monument in the first place. The answer: they were coming to eat spiders. The columns of the memorial were full of them. At night, the spiders would emerge and spin webs across the stonework. The next morning, the birds came to feast.

The question then became, why were there so many spiders? They were drawn by insects. Every evening, a thick cloud of midges arrived from the nearby marshes and swarmed around the monument, making it an all-you-can-eat buffet for the spiders.

At this point, someone suggested insecticides, but spraying poison across a national landmark wasn’t going to go down well with the public, or with Congress, or with the physical makeup of the structure itself.

So they did something smart; they continued asking questions. They brought in an entomologist named Donald Messersmith. Messersmith didn’t waste time on the birds, or the spiders, or even the midges. He looked at the lights. Every evening, just before sunset, the floodlights kicked on. They stayed on until well after dawn. Insects, being insects, flew toward the brightest source they could find. Which happened to be Abraham Lincoln’s face.

Messersmith’s suggestion was simple. Adjust the schedule. Turn the lights on a bit later in the evening, and switch them off earlier in the morning. They tried it. The midges dropped by eighty-five percent. The spiders vanished. The birds flew elsewhere. The droppings disappeared. The cleaning stopped; so, less strain on the marble.

It started as a problem with erosion. It ended with a conversation about insect behaviour and a change to the lighting schedule. That’s what happens when someone keeps asking questions after everyone else has packed up and gone home. Because sometimes it’s advantageous to be clever AND stubborn. If you want credit for solving a problem, stop looking for answers that are immediate and sound plausible. Look for the one that sounds illogical, and then proves that it isn’t.

And what it illustrates is something far more interesting than most people realise when they toss around phrases like “root cause.” Because the method behind the fix wasn’t some grand innovation. It was a refusal to accept the first answer. A refusal to believe that a problem shaped like a stain must have a solution shaped like a scrub brush.

This approach has a name. It’s called the Five Whys. It comes from Toyota, where engineers were trained to ask “why” five times in a row, each answer leading to another question, until you reach the actual root of the problem. On paper, it sounds like a neat little ladder. In practice, it’s usually abandoned halfway up.

Because the first “why” tends to be obvious, and the second is still within range. By the third, you’re in speculation. By the fourth, you risk looking daft. And the fifth, if you get there, almost always sounds unrelated. Which is precisely why it matters.

Someone willing to keep asking questions long after the answers stopped sounding professional saved the Lincoln Memorial. There’s nothing magic about the number five. The magic is in pushing past the plausible and arriving somewhere that would have sounded illogical at the start. The birds weren’t the problem. The spiders weren’t the problem. Even the midges weren’t the problem. The problem was light. But you’d never get there unless you were willing to ask something that felt ridiculous.

And that’s the point. The Five Whys reward the person in the room who doesn’t mind being annoying, or inconvenient, or just a bit slow to accept what everyone else has nodded through. The birds were nod-through logic. So were the spiders. So was the cleaning. It took someone not trying to look clever to follow the thread all the way to the floodlights.

That’s how good thinking works. It doesn’t arrive with a lanyard and a laminated chart. It sneaks in quietly through the back door, dressed as curiosity.