Pictured above is a jungle gym, a common installation on school playgrounds throughout the United States and likely the world. Jungle gyms (often called monkey bars) are a pretty straightforward — rods arranged in geometric shapes, designed so that children can swing and climb and, hopefully, not hurt themselves in the process. (Newer jungle gyms are often built on mulch and use PVC pipes instead of metal bars, for safety reasons.) Having such equipment available for school kids — safety concerns aside — is probably a good idea. A jungle gym can provide a lot of entertainment using a pretty small amount of space, all while requiring very little maintenance.

And it may help teach math.

Well, probably not — but that’s what it was originally intended to do.

In 1920, a man named Sebastian Hinton invented the structure — at least officially. Hinton was a Chicago-area lawyer who had more than a passing interest in education — his father was a mathematician and his wife was a notable educator. Somehow, Sebastian Hinton ended up at dinner with a school superintendent in Winnetka, Illinois named Carleton Washburne sometime that year. Washburne was looking at ways to introduce a “whole child” curriculum into his school. Hinton, independently, was building a climbing structure in his backyard for his children, and mentioned this to Washburne at their shared meal. As recounted by the Winnetka Historical Society, Washburne wanted to expand the amount of physical education during the school day and Hinton’s invention fit the bill. The Winnetka schools installed their own monkey bar sets shortly thereafter and Hinton applied for a pair of patents (here’s the first and here’s the second) for what he called “S. Hinton Climbing Structures.” He’d market it around the region and country thereafter.

So what does this have to do with math? For that, we have to go back a generation to what is probably the world’s first unofficial jungle gym — also in Hinton’s back yard, but in this case, at his father’s house when Sebastian was himself a kid. The older Mr. Hinton conceived the structure as a way to get his children thinking in terms of three dimensional space, and not just limiting themselves to the flat ground. The Winnetka Historical Society explained:

Mimicking a Cartesian-coordinate system [one of these] in mathematics, Hinton’s father named one set of horizontal poles X1, X2, X3, etc. Those horizontal poles at right angles to the X poles were Y1, Y2, Y3, etc., and the vertical poles he identified Z1, Z2, Z3, and so on. Hinton’s father would call out coordinates, “X2, Y4, Z3, Go!”, and the children would scramble for that intersection. Hinton said they humored their father with these drills, but what they really enjoyed was simply climbing, hanging, chasing, and playing like monkeys.

Sebastian Hinton had so much fun, it stuck with him through adulthood. He decided to build a jungle gym set for his kids — but decided to let them play, without insisting on adding in a math session.

Bonus Fact : The house from “Home Alone” and “Home Alone 2” is in Winnetka, Illinois, and last sold in 2012 for just under $1.6 million. The 4,243 square foot house has four bedrooms, four bathrooms, a finished basement, and a greenhouse, but it does not appear to have a jungle gym.

From the Archives: Tanks for the Info: How the Allies used a creative application of math to gain an advantage in World War II.

Related: A jungle gym for your backyard, if you’re so daring. This one is shaped like a geometric dome, so it isn’t all that useful for teaching Cartesian coordinates.