If you have served federal active duty in the United States Armed Forces since December 7, 1941, and have been honorably discharged or are still serving - you are eligible for membership in The American Legion!
Because eligibility dates remain open, all active duty members of the U.S. Armed Forces are eligible to join The American Legion at this time, until the date of the end of hostilities as determined by the government of the United States.
U.S. Merchant Marine eligible only from December 7, 1941 to December 31, 1946 (WWII).
It is not necessary to have served over seas or in a combat area.
Eligibility FAQs: https://www.legion.org/membership/faq