A beloved piece of playground equipment is turning 100 years old. The history of the jungle gym and monkey bars is full of weird and and delightful twists, spanning from Japan to suburban Chicago.

Admissions totaled an estimated 1.3 billion in the U.S. and Canada last year, down from about 1.4 billion a decade ago. Many American moviegoers will no doubt balk at the idea of letting kids play ...

The history of the jungle gym, and its sibling the monkey bars, is full of weird and delightful twists and sub-plots that take us from Japan to suburban Chicago and delve into theoretical math.