After graduating from medical school ( Cornell University , 1981 ) , Jemison joined the Peace Corps . She served as its area medical officer from 1983 to 1985 in the West African countries of Sierra Leone and Liberia . After completing her medical , Jemison joined the staff of the Peace Corps and served as a Peace Corps Medical Officer from 1983 to 1985 responsible for the health of Peace Corps Volunteers serving in Liberia and Sierra Leone .