The 1939 New York World's Fair song "Dawn of a New Day" was written by George and Ira Gershwin. Unfortunately, I don't remember where I found the song so I can't give credit where credit is due. You can listen to the song here.

See also:
Railroads on Parade (1939)
All's Fair at the Fair (1938)
Memory of 'Tomorrow' (New York Times, 1941)
Donald Duck's "Modern Inventions" (1937)
Metal Man Comes to Life (1939)