After the end of World War I in 1918, 20 officers who had served in the American Expeditionary Forces were asked to suggest ideas for improving troop morale. One officer, U.S. Army Lieutenant Colonel Theodore Roosevelt, Jr., proposed an organization of veterans, the American Legion. After its formation in 1919, a number of existing women's organizations wanted to become the official affiliate of the Legion. The committee decided to create a new organization made up of the women most closely associated with the men of the Legion. This Auxiliary would perform those phases of Legion activities that were more suitably performed by women. In less than one year, 1,342 local units in 45 states of the Women’s Auxiliary to the American Legion had been organized.
In 2019, the American Legion's National Convention voted to replace the word "wife" with "spouse" in the organization’s constitution and bylaws section regarding eligibility to be a member of the American Legion Auxiliary; since then, male and female spouses of U.S. veterans have been eligible. Previously, only female spouses of U.S. veterans were.