Marion Post was born in Montclair, New Jersey in 1910. After studying at New York University she visited Europe where she heard Adolf Hitler speak in Berlin. Events in Nazi Germany turned her into a left-wing political activist.
On her return to the United States in 1933 Post attended lectures on photography at the Photo League. In 1937 she helped Paul Strand on his film on trade unions in the Deep South, People of the Cumberlands.
Post also worked as for a photographer for the Philadelphia Evening Post until Roy Stryker invited her to join the the federally sponsored Farm Security Administration. This small group of photographers, including Esther Bubley, Marjory Collins, Jack Delano, Arthur Rothstein, Walker Evans, Russell Lee, Gordon Parks, Charlotte Brooks, John Vachon, Carl Mydans, Dorothea Lange and Ben Shahn, were employed to publicize the conditions of the rural poor in America.
After her marriage to Lee Wolcott in 1941 she concentrated on bringing up her children. A joint exhibition with Esther Bubley was held at the Art Institute of Chicago (1989).
Marion Post Wolcott died in Santa Barbara, California in 1990.