Why was Oklahoma! considered a turning point in musical theatre?

Oklahoma! (1943) is widely considered a watershed moment in the history of musical theatre because it was the first truly "unified" musical.1

Unlike the musical comedies of its era, which often relied on a frenetic pace and a structure that prioritized individual songs over narrative, Oklahoma! established a new pattern where every element—including every line, song, and dance routine—served as an indispensable part of a closely-knit whole. By prioritizing dramatic substance and ensuring the story never strayed from its plot, the production successfully integrated music and narrative in a way that was then unfamiliar to the stage.123

Key factors in this transformation included:
* Narrative Integration: The show maintained a simple, engrossing story that allowed the plot to remain the primary focus.2
* Innovative Choreography: Agnes de Mille’s "Dream Ballet" provided serious psychological insight into the characters' desires and fears, elevating the role of dance beyond mere diversion.1
* Understated Presentation: The musical deviated from traditional conventions by utilizing an understated opening number, setting a new standard for the "golden age" of American musical comedy.1