Johnston's fame grew as a result of a few different things. Her artice "What a Woman can DoWith a Camera" was published in 1897.  She assisted with an exhibition by 28 female photographers in the 1900 called the Exposition Universelle.  In her thirties she became an avid traveller, photographing everything from coal miners to sailers being tattoed on board ships. In 1899 she photographed quite possibly her most successful series of works,  buildings and students of the Hampton Normal and Agricultural Institute.  This series was done to document the ordinary life of the school.

Hampdon Institute Science Class, 1899

From the 1920's on she became incresingly interested in photographing building and did an entire series of 247 shacks and mansions.  Soon afterwards, the University of Viginia hired her to photograph buildings in North Carolina in order to preserve its architectural history.

Old Dunbar Quarters, Falmouth

Her works have been purchased by the Met in New York, the Virginia Museum of Fine Arts, and the Baltimore Museum of Art. She continued to photograph until her death at the age of 88.