Musical comedies that are recognisably American in tone or theme predate the opening of Oklahoma! by many years. At the turn of the century, critics applauded the shows of George M. Cohan for the original, furiously quick-paced action and vernacular dialogue that were his trademarks. Other non-operatic popular plays of the era with appealing music began to feature more kinetic staging, homespun and believable (if often silly) characters, and an air of optimism and headstrong abandon. The singing and dancing actors of Cohan's type, masters and mistresses of the Triple Threat, bespoke a special brand of native entertainment as early as 1902. Fresh, clean, full of slangy humour and catchy songs, with plots loose enough to allow virtually any kind of specialty act to be inserted, truly American musical comedies like The Belle of New York (1897), Little Johnny Jones (1904; featuring the hit number ‘Yankee Doodle Boy’), or In Dahomey (1903; the first major African-American musical comedy to put ragtime songs on Broadway) established a type that became the standard through the 1920s.

Nevertheless, in the mid-twentieth century Oklahoma!, not merely a hit but an indisputable blockbuster of remarkable coherence, presented a new thematic direction and dramatic formula that marked yet another turning point for musical theatre and would be widely emulated. Oklahoma!'s popularity signalled a turn away from the contemporary and topical subjects preferred during the Depression Era in favour of a more sentimental style and subject. Historical subjects, especially nostalgic or patriotic American ones, could and would be portrayed on stage in a manner that avoided farce or parody. The legacy of Oklahoma! and successive hits by Rodgers and Hammerstein was multifaceted, but one of its most important elements was the book, or the story.