If you headed to Coney Island at the turn of the century, you might wade in the water, eat some ice cream, or try out a rollercoaster at the newly opened amusement park, Luna Park. But your boardwalk promenade might also include a visit to the equivalent of a fully functional neonatal intensive care unit, complete with incubators filled with sleeping, premature babies.

It wouldn’t be a fluke: babies in incubators were a common sideshow in the late 19th and early 20th centuries. Premature infants could be found at world’s fairs and in permanent exhibitions like the one at Luna Park. But the babies weren’t there to be on display—they were there to fight for their lives with the help of an intrepid German man, Martin Couney.

Couney used the most modern technology of his age, incubators, to keep preemies alive. But before his groundbreaking work, the technology was laughed at or dismissed by physicians.

Incubators for babies had been developed by Stéphane Tarnier, a French obstetrician who had seen them being used at a zoo. Tarnier adapted the idea he’d seen used on baby chicks for baby humans. But they were not widely adapted in the first years of their existence.

Part of the problem was the medical profession’s attitude toward premature babies. Caring for premature babies was expensive and, many thought, pointless. Babies born at a low birth weight were cared for, but mortality was high and physicians thought that Tarnier’s invention was unscientific. It was so new and unusual that few doctors believe in its life-saving potential.

Enter Pierre Budin, a French physician who wondered why more hospitals weren’t investing in incubators. Though he began conducting successful research with the technology in 1888, he ran into continual roadblocks when it came to getting support for incubators. So in 1896, he decided to display incubators at the Berlin World’s Fair.

At the time, fairs weren’t just places to take in rides or eat food. Starting in 1851, when Victorian-era Englanders staged the Great Exhibition, they were places for the world to gather and learn more about new, industrial-age technology. The Industrial Revolution had yielded new machines, devices and scientific discoveries, and they were important places for professionals and the public alike to learn more about the greatest discoveries of the time.

The 1896 World’s Fair was no exception. There, Martin Couney, a German man, saw a display of several premature babies Budin had acquired on loan from a Berlin hospital. Couney immediately realized that the unusual exhibit would save babies’ lives, and that the public would pay to see babies in incubators. The sight was so unusual that people crowded into the display, paying money while the doctors gave new life to the six infants.

The success of the exhibit made both Couney realize they had a potential lifesaver on their hands. (Though historians now believe he was not a medical doctor, he was interested in the care of premature babies because a daughter had been born prematurely.) If hospitals didn’t want to care for premature babies, Couney could, using fairs and exhibitions to draw crowds and money for their neonatal care.

At the time, Coney Island was a wonder in its own right. The beach and boardwalk had become a gathering place for pleasure-seekers, tens of thousands of whom visited every weekend of the summer. In response, a thriving culture of vendors, amusement providers and sideshows sprang up in amusement parks that dotted the beach. Coney Island’s appeal was made even more piquant by its relatively relaxed, casual atmosphere, where New York’s massive population could let their hair down and indulge themselves.

Starting in 1903, visitors could see a new attraction at Coney Island’s Luna Park: incubators. Couney moved permanently to the United States and opened two incubator exhibits, one at Luna Park and another at Dreamland, also in Coney Island. Nurses tended to babies as an enraptured public looked on. Like any other amusement, the premature baby exhibits included carnival barkers who tried to lure the public to come see the babies. Ticket proceeds went to help the preemies.

Couney ran the exhibits for decades, even enlisting his daughter Hildegard, the preemie who survived, to help at an Atlantic City incubator exhibit. He took the babies at no charge and received them from hospitals all over the country. Slowly, thousands of babies were nursed back to health, and all because the public loved seeing them warm and cozy in their incubators.

"It's strange, but as long as they saw me and I was alive, it was all right,” Lucille Horn, who was born prematurely in 1920, said in an NPR interview. "I think it was definitely more of a freak show. Something that they ordinarily did not see.” Horn lived to be 96. She was just one of the babies who survived; Couney claimed an 85 percent success rate and to have saved 6,500 babies over the course of his career.

Though the incubators had become a beloved sideshow, they were also serious medical business. In 1943, as more hospitals began to adopt incubators and his techniques, Couney closed the show at Coney Island. Today, one in 10 babies born in the United States is premature, but their chance of survival is vastly improved—thanks to Couney and the carnival babies.