Although there is some controversy regarding who was the first AAU Mr. America, because the contest Goodrich won allowed professionals and amateurs, it appears to me, and there are several mentions in the old mags supporting this, that the first AAU-endorsed Mr. America was the one in 1939 won by Roland Essmaker.
Strength & Health stated this on more than one occasion in the early years, then switched to indicating that Grimek was the first AAU Mr. America. Essmaker told me he had written to S&H asking why they were trying to re-write history, but got no satisfactory response.