The Advisory Committee on Immunization Practices (ACIP) is chartered as a federal advisory committee to provide expert external advice to CDC and the Secretary of the U.S. Department of Health and Human Services (DHHS) on the use of vaccines in the civilian population of the United States. This report summarizes the evolution of ACIP over the 50 years since its establishment in 1964 by the Surgeon General of the U.S. Public Health Service (USPHS).