The establishment of an Auxiliary to The American Legion was provided for by the first National Convention of The American Legion in 1919. By the time of the 1920 National Convention, 1,342 local Units of this Auxiliary had been formed; intensive organizational efforts were authorized. The first National Convention of the Auxiliary was held in Kansas City, Missouri, in 1921. At that time, the name “American Legion Auxiliary” was adopted and the first national officers elected.

The Auxiliary grew from a first year enrollment of 121,000 to approximately 500,000 at the beginning of World War II. After the women of World War II families became eligible, the enrollment rose rapidly to a record of 1,001,545 in 1955, and since has remained around the 800,000 mark. The number of local Units of the Auxiliary is approximately 9,500. The Auxiliary organization (i.e., local, state and national) parallels that of The American Legion. Auxiliary National Headquarters is located in Indianapolis, Indiana.