Ebony magazine was founded in 1945 to serve the African-American community.  This quotation from a Vietnam War article was printed in August 1968:
     
“Here a lanky, Brooklyn draftee stated: ‘I’m gonna stay alive, you hear me? I’m gonna stay alive and get back to the big apple. I didn’t lose a damn thing here in the Nam and I ain’t staying a minute longer than I have to.’”
   
This citation is before the New York Convention and Visitors Bureau repopularized “Big Apple” in the 1970s.
   
 
Wikipedia: Ebony (magazine)
Ebony is a monthly magazine that focuses on news, culture, and entertainment. Its target audience is the African-American community, and its coverage includes the lifestyles and accomplishments of influential black people, fashion, beauty, and politics.
 
Ebony magazine was founded in 1945 by John H. Johnson, for his Johnson Publishing Company.
 
Google Books
August 1968, Ebony, “Negroes in ‘The Name’” by Thomas A, Johnson, pg. 32, col. 2:
Here a lanky, Brooklyn draftee stated: “I’m gonna stay alive, you hear me? I’m gonna stay alive and get back to the big apple. I didn’t lose a damn thing here in the Nam and I ain’t staying a minute longer than I have to.”
 
Google Books
July 1969, Ebony, “Duke Ellington: he took the ‘A’ Train to the White House” by Phyl Garland, pg. 31, col. 1:
Jaz was a somewhat different thing from the harmonically rich and greatly varied music we know today, back in 1922 when a handsome young Washingtonian, already called “the Duke,” made his first sally into the “Big Apple” of New York City.