She was the first woman to enlist in the US Marine Corps and her enlistment helped pave the way for future generations of women to serve in the Marine Corps and other branches of the US military.

• On August 13, 1918, Johnson became the first woman to enlist in the US Marine Corps, shortly after the US government authorized the enlistment of women for clerical duties during World War I.
  
• She was assigned to the Marine Corps headquarters where she served as a clerk and typist. She was one of over 300 women who served in the Marine Corps during World War 1.
  
• Opha May Johnson died on August 11, 1955 at the Mount Alto Veterans Hospital in Washington, D.C. Her services were delayed two days until August 13, 1955, which was 37 years to the day from when she answered the call to become a U.S. Marine.
  
• Recognizing her historic service, the Marine training center at Grissom Air Reserve Base was renamed the Sergeant Opha May Johnson Marine Reserve Center on November 10, 2022, which was the 247th anniversary of the founding of the Marine Corps.