While the atrocities committed by the Nazis under the guise of medical research during (and before) World War II are well known, and often taught in high schools and colleges, less well studied are the medical research scandals that have been discovered in the United States over the past 50 years. These include the Jewish Chronic Hospital Disease case, in which live cancer cells were injected into elderly patients without informed consent; the Tuskegee Syphilis Study, where the United States Public Health Service conducted a natural history study of syphilis in the "Negro male" for 40 years, specifically withholding knowledge of and treatment for the disease from the participants; and the Willowbrook Institution case, in which mentally retarded children were injected with hepatitis virus without their parent's or guardian's consent. That these were not isolated incidents at that time (the 1960s and 1970s) can be seen in an article from the New England Journal of Medicine (NEJM, 274(24):1354-1360).
The evidence that unethical medical research was being performed in the United States led to the creation by the Federal Government of a National Commission for the Protection of Human Subjects of Biomedical and Behavioral Research, which produced a report on the “Ethical Principles and Guidelines for the Protection of Human Subjects in Research" (the “Belmont Report” http://ohsr.od.nih.gov/guidelines/belmont.html ). This report forms the basis for current Federal Policy for the protection of human subjects in research.
This timeline is succinct in giving an overview of the History of Human Subjects Protection in the United States (credit is given to the State of Washington from one of its publications). And here is an article about bioethics.