When Johnston was 16, her father's work with the Georgia Pacific Railroad caused the family to move to Birmingham, Alabama.

The Goddess of Reason (1907) uses the theme of the French Revolution, and in Lewis Rand (1908) the author portrayed political life at the dawn of the 19th century.

Johnston's next work, titled Audrey, was the fifth bestselling book in the U.S. in 1902, and Sir Mortimer, serialized in Harper's Monthly magazine from November 1903 through April 1904, was published in 1904.

Her book titled Hagar (1913), considered to be one of the first feminist novels as well as somewhat autobiographical, captures the early days of women's rights.

Johnston's deep focus on female suffrage in the United States is documented by her letters and correspondence with women working for the right to vote.

[2][3] Johnston was an early an active member of the Equal Suffrage League of Virginia (ESL), which was founded in November 1909 by other Richmond-area activists like Lila Meade Valentine, Ellen Glasgow, and Kate Waller Barrett.

[5] On December 12, 1909, the Richmond Times-Dispatch published a pro-suffragist article written by Johnston entitled “The Status of Women.” The ESL would go on to reprint this article, along with another entitled "These Things Can Be Done" in Virginia Suffrage News, a monthly paper created to increase communication among the suffrage leagues across the state of Virginia.

She also spoke at the closing event of the 1913 Woman Suffrage Procession in Washington, D.C.[5] In 1936, Johnston died of Bright's disease at her home in Warm Springs, Virginia.

[14] Johnston's name is featured on the Wall of Honor on the Virginia Women's Monument, located in Capitol Square in Richmond.