The Wikipedia article on Santa Catalina Island says that songwriter Harold Spina published his song "Santa Catalina (Island of Romance)" in 1946. The song was performed and recorded by many pop artists including Tony Martin, Dorothy Collins, Gordon Jenkins and His Orchestra, The Modernaires, Eddy Howard and His Orchestra, Freddy Martin and His Orchestra, and several others.

I had trouble tracking down this forgettable song, but finally found a recording by the Dinning Sisters:

https://www.youtube.com/watch?v=e2m_2Y5DNng

And here's a forgettable 1947 recording by Eddy Howard:

https://www.youtube.com/watch?v=BHPV5iuCrUY