Margaret D. Foster (March 4, 1895 – November 5, 1970) was an American chemist. In 1918, she became the first female chemist to work for the United States Geological Survey, developing ways to detect minerals within naturally occurring bodies of water, and was recruited to work on the Manhattan Project during World War II, developing new techniques of quantitative analysis for the radioactive elements uranium and thorium. This photograph depicts Foster working with chemicals in a laboratory in 1919.Photograph credit: National Photo Company; restored by Adam Cuerden