Leonard Lee Bailey (1942–2019) was an American surgeon who garnered international media attention in 1984 for transplanting a baboon's heart into a human infant. Bailey was born on August 28, 1942, in Takoma Park, Maryland. In 1964, he graduated from Columbia Union College, and he earned a medical degree from Loma Linda University, School of Medicine in 1969. During the 1970s, during his residency at Toronto's Hospital for Sick Children, Bailey observed that many children died from congenital heart diseases. This led him to return to Loma Linda University in 1976 as assistant professor at the School of Medicine. There he performed more than 200 experimental heart transplants on young mammals so he could see if there was the possibility of transplantation in young mammals.