'The Wizard of Oz' without 'Over the Rainbow' would be like 'The Bodyguard' without 'I Will Always Love You' or 'Titanic' without 'My Heart Will Go On'. The song is such a big part of the film that the two are linked in the minds of everyone who's seen it. And yet it nearly ended up on the cutting room floor.
The team of MGM Directors behind the picture were worried that the song was too long, and that younger viewers would get bored by it. Fortunately, common sense prevailed, and it stayed in the final edit. The song would go on to be ranked as the greatest movie song of all time by the American Film Institute, and has been preserved by the Library of Congress, who have marked it as 'culturally, historically or artistically significant'. Judy Garland included the song in her performances all the way up to her death in 1969.