Which musical first performed in 1943 ushered in the Golden Age of Book Musicals?

The musical that first performed in 1943 and is often credited with ushering in the Golden Age of Book Musicals is "Oklahoma!" by Richard Rodgers and Oscar Hammerstein II. This groundbreaking production integrated songs and story in a cohesive narrative, setting a new standard for musicals. Its success marked a shift towards more sophisticated and plot-driven musical theater. "Oklahoma!" is widely regarded as a turning point in the evolution of the American musical.