Eventually, she got to wondering about its story. Thornton started scouring old newspapers and found a truly bizarre answer from the early 1900s. The building was part of a short-lived but fantastical amusement park called "Wonderland."

There, buttoned-up, turn-of-the-century guests could let loose on the log flume or the carousel, gawk at the newfangled electric lights, or stroll through a so-called “house of nonsense.” But its most popular attraction was housed in the same old apartment that originally caught Thornton’s eye.

Welcome to the "Infantorium," one of a proud handful of amusement park attractions of its kind scattered across the United States and Europe. There, guests could marvel at a suite of real, live premature babies in glass incubators.

We understand you have questions. The first might be “Why are these babies in a sideshow exhibit instead of being taken care of in a hospital?” The sad answer was, though a fairly simple and effective incubator had already been developed by doctors in France, American hospitals weren’t especially interested in treating premature babies.

The turn of the century was the heyday of America's eugenics craze and all of the racist, ableist, and otherwise toxic ideologies that came with it. Editorials argued allowing a baby that couldn’t survive without medical intervention to grow to adulthood would somehow weaken the national gene pool. Better, eugenicists surmised, to let them die.

If parents wanted their preemie babies to live, they had to bring them to Dr. Martin Couney, who would display the child in one of his incubator attractions. It sounds macabre, but Courney hired real wet nurses, never charged the parents a dime, and took in babies of all races and ethnic backgrounds.

The vast majority survived and were returned to their parents at the end of the fair season, an accomplishment in an era when premature babies had a 75 percent mortality rate.

At Wonderland’s Infantorium, some guests would return week after week to see how their favorite babies were coming along. Nurses lived onsite in the rooms upstairs, now apartments for modern-day tenants.

The public was weirdly fascinated with watching these fragile babies survive in glass boxes. Katie Thornton, Instagram

Thornton delves into this strange, largely forgotten chapter of medical history in great detail on a recent episode of the popular 99% Invisible podcast. Wonderland’s tenure was short-lived (1905-1911), but even on a national scale, the fact that fragile babies were carnival attractions all over the country hasn’t permeated the cultural memory.

“I don’t know if it’s because it’s in some ways shameful or uncomfortable to discuss,” Thornton says. It is in many ways, after all, a story about a healthcare system so callous that parents were forced to let their babies be exploited for the amusement of the public. (Couney may not have even been a real doctor.)

In many ways, Thornton says, our health care system is still exploitative.

“It’s really made me think a lot about what future generations will think about our current medical practices,” she says. “Today, there are still people profiting off of other people’s illnesses.”

Couney would continue to display babies in various amusement parks, and continually ask public health departments and hospitals to start using his machines. But it wouldn’t be until after he died in 1950—obscure and pretty much penniless—that incubators would become common in maternity wards.

Nonetheless, there are still people alive today because they spent their first weeks on display in one of Couney’s establishments. Thornton spoke to one, Beth Allen, on the podcast episode. Regardless whether Couney was a saint or a sideshow hack, they got to live full, healthy lives. That’s something Thornton thinks about a lot.

“My brother was born incredibly early in Minneapolis, outside the fair season,” she says. If he’d been born 75 years ago, he may not have been so lucky.

For more insights on Wonderland and the Infantorium, check out Thornton’s Instagram feed.