Doctor injecting a patient with placebo in the infamous Tuskegee Syphilis Study.

Doctor injecting a patient with placebo as part of the Tuskegee Syphilis Study.

From the CDC:
Tuskegee Study, 1932-1972
Nearly 65 years after the U.S. Public Health Service Syphilis Study at Tuskegee began, President Clinton apologized for the U.S. government’s role in the research study, which was carried out in Macon County, Alabama, from 1932 to 1972.

The United States Public Health Service, in trying to learn more about syphilis and justify treatment programs for blacks, withheld adequate treatment from a group of poor black men who had the disease, causing needless pain and suffering for the men and their loved ones.

In the wake of the U.S. Public Health Service Syphilis Study at Tuskegee and other studies, the federal government took a closer look at research involving human subjects and made changes to prevent the moral breaches that occurred in Tuskegee from happening again.

https://www.cdc.gov/tuskegee/index.html