What Is the Steepest Hill?

If you’ve ever walked up a hill steeper than you expected it to be, you might have found yourself winded and then struggled to pretend you were completely fine because how humiliating is it to be defeated by an inanimate incline? Just us? Well good for you, but what is the steepest hill?

Further Reading: What’s the Difference Between Hills and Mountains?

Steep Streets

Let’s start with places you might reasonably find yourself. The “steepness” of a hill is its grade (gradient), which is represented as a percentage. If you turn a slope into a right triangle, where the incline itself is the diagonal, a street or hill’s grade is a percentage equal to the height divided by the width of the triangle. You could also say it’s the tangent to the incline’s angle. 

Anyway, this percentage can get a little weird with streets, since a 100% grade is actually a 45 degree angle, and a 0% grade is completely flat. This does mean a slope can have a grade over 100%; a 47.7 degree angle would give you a 110% grade. A perfectly vertical slope approaches infinity. All you really need to know is that 100% is a 45 degree angle. 

In the US, the federal limit for highway steepness is 6%. Because it’s a federal limit, though, it only applies to highways that cross state lines. But that 6% is just about a 3.4 degree angle. This does mean that, within individual states, we can find streets much steeper. 

California in particular is known for its steep streets, so if you thought it was just you who felt that way you’re probably not alone. You might have heard of Filbert Street with a 31.5% grade in San Francisco. Sometimes it’s advertised as the steepest in California, but it’s not even the steepest in San Francisco if you split hairs. An unofficial survey found the steepest parts of some streets push 37% or even 41% grade. 

The steepest street in the USA is Waipio Valley Road, which you can find in Hawaii. On average, its grade is 25% but peaks at 45%, which is a 24 degree drop. If you rent a car in Hawaii, there’s actually a pretty good chance they’ll make you agree to not drive through Waipio Valley Road. 

If you ask the Guinness World Records people, they’ll tell you the steepest street is Baldwin Street—which you’ll find in New Zealand at about a 35% grade. 

Thor

Alright, but you came here looking for the steepest hill. Not the steepest street. At this point you’re really just looking at cliffs, which can be parts of mountains or hills. 

So what’s the steepest one? You can find it on Baffin Island, which is also the largest island in Canada. Famously, you’ll find Mount Asgard here, but apparently Asgard is no match for Mount Thor.

Mount Thor is home to Earth’s greatest vertical drop, if you were to jump off you’d fall about 4,100 feet. If you weigh 175 pounds, you’d be falling for almost a full 26 seconds before you hit the ground. You might think the drop is 90 degrees, and that’s why it’s the steepest. It actually comes in at a 105 degree overhang, which is, we guess, steeper than being vertical. 


Speaking of hills, see if you know the seven of Rome here.

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