“Big Apple as mecca” (Jet magazine, 1952)

Jet magazine was founded in 1945 to serve the African-American community. “Big Apple” was cited many times.
   
“From the South and Midwest, beauty queens look to the ‘Big Apple’ as mecca and migrate to Harlem to seek their fortune” was printed on June 5, 1952. “It was his first trip back to the ‘Big Apple’ (New York City—ed.) in 25 years” was printed on October 30, 1958.
         
These citations of “Big Apple” are before the New York Convention and Visitors Bureau repopularized “Big Apple” in the 1970s.
         
     
Wikipedia: Jet (magazine)
Jet is an American weekly digital magazine focusing on news, culture, and entertainment related to the African-American community. Founded in November 1951 by John H. Johnson of the Johnson Publishing Company in Chicago, Illinois, the magazine was billed as “The Weekly Negro News Magazine”. Jet chronicled the civil rights movement from its earliest years, including the murder of Emmett Till, the Montgomery bus boycott, and the activities of civil rights leader Martin Luther King Jr.
       
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5 June 1952, Jet, “Harlem Versus Hollywood,” pg. 33:
From the South and Midwest, beauty queens look to the “Big Apple” as mecca and migrate to Harlem to seek their fortune — whether as a ...
     
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10 June 1954, jet, pg. 59 (photo caption):
‘Big Apple’: After their closing performances in the summer musical Showboat at New York City Center, show’s star Berl Ives (1.) and baritone Lawrence Winters share last apples together backstage.
   
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17 February 1955, Jet, “Inside Sports” by A. S. “Doc” Young, pg. 57: 
There was a time when it appeared that he would freeze to death in the cold caverns of the Big Apple.
     
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19 May 1955, Jet, “People Are talking About,” pg. 46:
That Big Apple cop whose wife tried to run over him with her car then left him to die in the street.
 
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30 October 1958, Jet, pg. 38:
TRAVELOGUE Clarence Callicoatte. former Harlemite and a 20-year man in the engineering department of Los Angeles’ Edison Co., took his wife Mildred to New York for a two-week holiday. It was his first trip back to the “Big Apple” in 25 years