Sergeant Johnson worked for the Interstate Commerce Commission until 1918, when the U.S. Marine Corps opened enlistment to women.
On August 13, 1918, she was the first woman in line to enlist, thus becoming the first woman to be called a U.S. Marine.
She was assigned to clerical duties at Marine Corp headquarters.
Discharged at the end of the war, she went on to work for the war department, still serving the Marine Corps, until her retirement in 1943. Sergeant Johnson died on August 11, 1955, and rests in Rock Creek Cemetery.