Membership in the American Legion, the World's largest Veterans Service Organization, is open to any US Military veteran that served at least one day of Active Duty during one of the following periods:

 

April 6, 1917 - Nov. 11, 1918.

 

Dec. 7, 1941 until cessation of hostilities as determined by the US Gov't.

 

Also, Merchant Marines between Dec. 7, 1941 and Aug. 15, 1945.