Who was the first woman in the Marine Corps?

Opha Mae Johnson holds the distinction of being the first woman to enlist in the United States Marine Corps. She joined in 1918 during World War I when the demand for military personnel was high. Her enlistment marked a significant milestone in the integration of women into the armed forces, as she paved the way for future generations of female Marines. Johnson's contributions and service led to a broader acceptance of women serving in combat and support roles within the military.

In contrast, while the other individuals mentioned played important roles in military history or are notable figures in various capacities, they did not have the precedent-setting role that Opha Mae Johnson had in the Marine Corps. For instance, Margaret Chase Smith served as a U.S. senator and was a significant political figure, but she was not a member of the Marine Corps. Helen W. N. Ambrose is typically known for her contributions to the drawing of women into military branches much later, and Barbara K. Healy has her own achievements but is not recognized as a pioneer like Johnson. Thus, Opha Mae Johnson's role as the first woman to enlist in the Marine Corps is crucial in understanding the history and evolution of women's involvement in the military.