America's first hospitals for premature infants were built at the turn of the twentieth century at fairs, amusement parks, and expositions. These hospitals represented both a medical and a social frontier. They had a great impact on American medicine because they demonstrated the success of caring for premature infants using incubators. The incubator hospitals were a social frontier, because they challenged many of the social norms of the time, providing affordable care while marketing their product and making a large profit. The hospitals also had an impact on society as a whole because the public was exposed to new technology, which greatly improved the care of premature infants. This article presents the history of American incubator hospitals. (Contains 2 figures and 21 resources.)