The American Legion was established on March 15, 1919, in Paris, France, by delegates to a caucus meeting from units of the American Expeditionary Forces (A. E. F.), which adopted a tentative constitution. The action of the Paris Caucus was confirmed and endorsed by a similar meeting held in St. Louis, Missouri, from May 8 to 10, 1919, when the Legion was formally recognized by the troops who served in the United States.

The Paris Caucus appointed an Executive Committee of seventeen officers and men to represent the troops in France in the conduct of the Legion. The St. Louis caucus appointed a similar Committee of Seventeen. These two national executive committees amalgamated and were the initial governing body of the Legion. The temporary headquarters was located in New York.