Johnson's career began as a teacher in Ohio, North Carolina and Kansas City. Johnson taught at the State Normal School for Negroes in North Carolina and then was also the Dean of Women at Shorter College in Little Rock, Ark. in 1906. While teaching in a high school, Johnson joined the National Association for the Advancement of Colored People as one of the first members when it was first formed in 1909. During her time in the association, Johnson was a sales representative for the NAACP's journal, TheCrisis. As a branch organizer in the association, she was also responsible for helping dozens of branches of the association throughout the south. However, Johnson began to criticize that the NAACP failed to have any colored people as leaders so Johnson left the association in 1916. Johnson joined the Young Men's Christian Association. In the YMCA, Johnson worked amongst African Americans. The YMCA ended up sending Johnson and her coworker, Addie Waites Hunton, to France. In France, they were responsible for examining the treatment of black soldiers during World War I. Once they returned home, the two of them wrote the book Two Colored Women with the American Expeditionary Forces. The book described the poor treatment black soldiers observed in the cultural climate of France during the war.
Later life and legacy
Johnson's mission after returning from France was to spread activism against racial oppression by promoting literacy. Johnson began a nationwide campaign to help improve the civil rights through promoting literacy. This included selling books from black authors called "A Two Foot Shelf of Negro Literature" and selecting and circulating literature by Carter G, Woodson, W. E. B. Du Bois, Benjamin Brawley and James Weldon Johnson. By being a bookseller, Johnson hoped to promote reading among African Americans in order for them to learn more about their historical contributions and hopefully to then inspire them to take action in fight against racial oppression. Over the years, Johnson had traveled over "9,000 miles and sold 15,000 books." Johnson's work also helped showed the possibilities as well as restrictions that African American women had during this time period. During her old age, Kathryn Magnolia Johnson lived in Ezella Mathias Carter Home for Colored Working Women in Chicago. Johnson died on November 13, 1954.