A Grafton native, she was a pioneering figure in portraiture, photojournalism, and documentary photography at a time when the field was dominated by men. Starting as a photojournalist, she captured labor in New England shoe factories and became one of the first women recognized as a press photographer. Her photos of figures like Susan B. Anthony, Mark Twain, and presidents solidified her prominence.

Her work with Booker T. Washington led her to document African American life at Hampton and Tuskegee Institutes. Johnston’s photographic survey of the early American South, capturing plantation homes and post-Civil War impacts, remains highly regarded, with her work held in institutions like the Library of Congress and Museum of Modern Art.