Alice Hamilton (February 27, 1869 - September 22, 1970) was an American physician, research scientist, and author who is best known as a leading expert in the field of occupational health and a pioneer in the field of industrial toxicology. She was also the first woman appointed to the faculty of Harvard University. Her scientific research focused on the study of occupational illnesses and the dangerous effects of industrial metals and chemical compounds. In addition to her scientific work, Hamilton was a social-welfare reformer, humanitarian, peace activist, and a resident-volunteer at Hull House in Chicago.

In January 1919 Hamilton accepted a position as assistant professor in a newly-formed Department of Industrial Medicine (and after 1925 the School of Public Health) at Harvard Medical School, making her the first woman appointed to the Harvard University faculty in any field. Her appointment was hailed by the New York Tribune with the headline: "A Woman on Harvard Faculty--The Last Citadel Has Fallen--The Sex Has Come Into Its Own". Her own comment was "Yes, I am the first woman on the Harvard faculty--but not the first one who should have been appointed!"  During her years at Harvard, from 1919 to her retirement in 1935, Hamilton never received a faculty promotion and held only a series of three-year appointments. At her request, the half-time appointments for which she taught one semester per year allowed her to continue her research and spend several months of each year at Hull House. Hamilton also faced discrimination as a woman. She was excluded from social activities, could not enter the Harvard Union, attend the Faculty Club, or receive a quota of football tickets. In addition, Hamilton was not allowed to march in the university's commencement ceremonies as the male faculty members did.  Hamilton became a successful fundraiser for Harvard as she continued to write and conduct research on the dangerous trades. In addition to publishing "landmark reports for the U.S. Department of Labor" on research related to workers in Arizona copper mines and stonecutters at Indiana's limestone quarries, Hamilton also wrote Industrial Poisons in the United States (1925), the first American textbook on the subject, and another related textbook, Industrial Toxicology (1934). At tetraethyl lead conference in Washington, D.C. in 1925, Hamilton was the most prominent critic of adding tetraethyl lead to gasoline.  Hamilton also remained an activist in social reform efforts. Her specific interests in civil liberties, peace, birth control, and protective labor legislation for women caused some of her critics to consider her a "radical" and a "subversive." From 1924 to 1930, she served as the only woman member of the League of Nations Health Committee. She also visited the Soviet Union in 1924 and Nazi Germany in April 1933. Hamilton wrote "The Youth Who Are Hitler's Strength," which was published in The New York Times. The article described Nazi exploitation of youth in the years between the two world wars. She also criticized the Nazi education, especially its domestic training for girls.Answer this question using a quote from the following article:

How long did she teach at Harvard?
1919 to her retirement in 1935,