Fred Zinnemann’s Oklahoma! is an adaptation of Richard Rodgers and Oscar Hammerstein II’s Oklahoma! (1943) is an adaptation of Lynn Riggs’ Green Grow the Lilacs (1931). 
Hammerstein wrote one (Act 2) to intensify the rivalry between Curly McClain and Jud Fry for Laurey Williams. Riggs’ Green Grow the Lilacs has a party without a box social and basket auction. It follows the stylized square dance and the song “The Farmer and the Cowman should be Fiends.” Presumably, this is an ironic reference to Curly, a cowboy, and Jud, a farmhand. Neither of whom will ever be friends.
IKE: (After the number is over) C’mon, everybody! Time to start the Box Social.
CORD ELAM: I’m so hungry I c’d eat a gatepost.
GIRL: Who’s goin’ to be the auctioneer?
ALL: Aunt Eller!
Bidding for Laurey begins when Jud offers “a dollar and quarter.”
The basket auction is a substitute for lovers’ combat. Good-hearted Curly and black-hearted Jud bid for the basket that is a symbol of Laurey. Each man knows that the winner takes all. Laurey is just chattel. Laurey, dressed in virginal white, is helpless. She is afraid and attracted to Jud’s physicality and sexuality. Still, she favors Curly, who repays her favor by selling his saddle, horse, and gun to win her: “Going, going, gone,” says the auctioneer Aunt Eller. “Well, what’s the matter with you folks? Ain’t nobody gonna cheer or nothin’.”
Shirley Jones as Laurey Williams and Rod Steiger as Jud Fry
See Fred Zinnemann. Oklahoma! (1955). The screenplay by Sonya Levien and William Ludwig is based on Richard Rodgers and Oscar Hammerstein, II. Oklahoma! (1943) and Lynn Riggs. Green Grow the Lilacs (1931); Lynn Riggs. Green Grow the Lilacs. In The Cherokee Night and Other Plays. Norman, Oklahoma: University of Oklahoma Press, 1936. Reprint, 2003. Also, other productions by Rouben Mamoulian (1943); Trevor Nunn (1999), and Daniel Fish (2019).