Just like the weird connection American culture had in depicting blacks running away from alligators (see alligator postcards in this collection), they also commonly associated African Americans with watermelon.
Undated. “Get a Load of This!” Front of postcard shows a man holding a shotgun on a black man happily stealing a watermelon.
1905 “We’s In Heben“. Front of postcard says “Copyright 1897 by F.L. Howe”, but postcard is postmarked 1905.
1908 “A Study In Black and Red”
1908 “If the Man in the Moon Were a Coon“: This racist postcard, postmarked 1908, shows a moon with exaggerated facial features and staring at watermelons. Very good condition.
1940 “Anticipation-Down in Sunny Dixie” and shows an older man directing a child to reach a watermelon through a fence. This E.C. Kropp Co. card has a one cent stamp and Oct 13, 1940 Charleston, S.C. postmark.
Civil Rights Heritage Museum Online 