First appearance: All-American Comics #19 (October 1940).
NOTE: Golden Age Green Lantern Alan Scott had debuted in issue #16
He was also a founding members of the Justice Society of America.
Both he and Hawkman were the only two heroes who were continuous full-time members during the Justice Society of America's Golden Age run, from All Star Comics #3 through issue #57 (cover-dated February-March 1951).
And from Who's Who: The Definitive Directory of the DC Universe Vol. I (March 1985),