Gymnastics foam pits were first. Ball pits soon after.
The invention of the ball pit (or “ball crawl,” as it was first dubbed) is widely attributed to Eric McMillan.
… In 1971, he was appointed chief designer of Ontario Place, an ambitious project that included a park, theme park, and the world’s first IMAX theater on newly built artificial islands just off the Toronto waterfront. Ontario Place was a visionary project, but it was missing something.
Striving for a more kid-friendly environment, the designer created The Children’s Village, a massive playground unlike any other, where youngsters could climb huge rope nets and soft pyramids, crawl through hanging tunnels, and jump on an enormous air mattress. “The Children’s Village opened in July 1972 …
McMillan did not install a ball pit in Toronto, however.
According to McMillan, that honor belongs to the ball crawl he installed in 1976 at SeaWorld Captain Kids World in San Diego, another of a handful of theme parks McMillan designed …
How the indoor playground became a staple in our safety-obsessed culture