The Jungle Gym Started as a Math Experiment

Charles Howard Hinton was a fringe figure in history—publishing a few books on the fourth dimension, patenting a gunpowder-powered baseball pitching machine and dabbling in early science fiction. Yet this British mathematician’s most enduring legacy lives on in a fixture familiar to generations of children: the playground jungle gym.

Hinton moved in intellectual circles of the late 19th century while studying at Oxford and teaching at Uppingham College in Rutland, England. In 1880, he married Mary Ellen Boole, a daughter of George Boole (whose system of logic underpins the foundation of modern computing). During this period, Hinton developed a series of color-coded wooden cubes, which he arranged and memorized in shifting configurations. His goal was to train his mind to perceive all facets of the cube set simultaneously—what he described in A New Era of Thought (1888) as “a direct feeling of what the block is.” Hinton's manipulation of these cubes led him to visualize a concept beyond the three-dimensional world we experience of length, width and depth.

As Hinton rotated the cubes in various directions, something unexpected emerged: a glimpse of a higher-order shape, a four-dimensional form that he called a “tesseract” (or “tessaract” in earlier writings). “Consider for a moment what happens to a square when moved to form a cube. Each of its lines, moved in the new direction, traces a square; the square itself traces a new figure, a cube, which ends in another square,” Hinton wrote. This geometric representation of a cube extended into multiple directions illustrates the concept of four dimensions.

He introduced the cubes to his wife’s younger sisters, but only one embraced them: a teenaged Alicia Boole Stott (who went on to become a gifted mathematician in her own right). Hinton continued to experiment with ways to teach the concept.

After a fall from grace in England following a conviction for bigamy, Hinton moved his family to Japan. He became headmaster of a school in Yokohama, serving the children of British expatriates. He also brought along his wooden cubes and further developed his method for visualizing higher dimensions. Hinton instructed students to imagine sets of cubes as a house, with each cube representing a piece of furniture; then he challenged them to map out different routes through the imagined three-dimensional gridded landscape. 

At home, Hinton built a real gridded landscape—a climbable multi-cube frame made from bound bamboo sticks—to help his sons grasp three-dimensional space. Convinced that mastering the third dimension would prepare them for the conceptual leap to the fourth, Hinton called out Cartesian coordinates (X2! Y4!) to direct the boys where to climb. 

Decades later, Sebastian Hinton—one of Charles Hinton’s sons and a patent attorney—admitted at a dinner party that he never cared much for the geometric intent of his father’s frame; he simply loved climbing on it. This idea immediately intrigued Carleton Washburne, who was not only seated at the table, but was the school superintendent in Winnetka, Illinois.

An advocate of progressive education, Washburne saw the climbing frame as “an ideal piece of school playground equipment,” he later wrote in Winnetka: The History and Significance of an Educational Experiment (1963). It offered children a chance to challenge themselves both physically and mentally, each at their own pace—fitting right into his educational vision. “It can take care of many children in a small area. It satisfies every child’s desire to climb. It exercises all the muscles,” he added.

Wasting no time, Hinton, Washburne and Perry Dunlap Smith—headmaster of Winnetka’s North Shore Country Day School—began to sketch out a prototype. Shortly afterward, they built a model from iron pipes and installed it on the school grounds. It proved hugely popular, and the trio made adjustments to their design before installing the first permanent jungle gym at the Horace Mann School. (When the school faced demolition in 1940, the original structure was preserved and relocated to the Crow Island School, where it remained in use for more than nine decades.)

In 1920, Hinton submitted a patent application for the climbing apparatus, which he envisioned as providing “a kind of forest top through which a troop of children may play in a manner somewhat similar to that of a troop of monkeys,” he wrote. He also launched the company Junglegym, Inc. to manufacture and distribute the structure to schools across the country. But he would never see the patent approved. Hinton was soon hospitalized for depression and died in April 1923—just a few months before the patent was granted.

Nevertheless, the jungle gym—and its later plastic and roped variations—became a staple of playgrounds across the United States. The first American playground, established in Boston in 1885, was essentially just a sandpile, notes Alexandra Lange, author of The Design of Childhood: How the Material World Shapes Independent Kids. She explains that these “sand gardens” were conceived as a public good—a means of protecting the young children of recent immigrants from increasingly crowded and dangerous streets—with equipment later added to serve a wider age range of children. 

“The jungle gym wasn't the first type of playground equipment—playgrounds with swings and seesaws existed in the later 1880s—but it was one of the most distinctive,” Lange says. “One of the strengths of the design is that you can climb in any direction, and the gridded structure could break your fall. It’s also occupiable. Kids can pretend-play inside a jungle gym as if it were a house, or a train or a shop window.”

Every time a child scrambles through a jungle gym then, imagining it as a house or secret fort or even just swinging from bar to bar, they’re unknowingly carrying on Charles Hinton’s original vision—grasping the third dimension through imagination and motion.