Dana Andrews's singing voice was dubbed by radio singer and announcer Ben Gage, who at one time was married to Esther Williams. The studio was unaware that Andrews was a trained singer. He later explained that he didn't correct the oversight because he figured the ghost singer also needed to earn a living and he didn't want to deny his colleague employment. Ironically, despite his training, in a film career that lasted three decades, Andrews never displayed his singing voice on screen.
Harry Morgan (billed as Henry Morgan) appears as a dishonest carnival barker. Morgan went on to play Colonel Sherman Potter in M*A*S*H (1972). In the 11th season episode, The Moon Is Not Blue (1982), the staff of the M*A*S*H 4077th unit watches "State Fair".
Based on their individually sour experiences in Hollywood during the 1930s, Richard Rodgers and Oscar Hammerstein II consented to compose the score for State Fair (1945) only if they could do so without having to set foot in California. Therefore, the team wrote the songs in New York, shipped them to the studio and bowed out --- that is, until Rodgers caught wind of the fact that musical director Alfred Newman planned to conduct "It Might As Well Be Spring" as a moody, expansive ballad. Rodgers fought the studio on this one point, as he had specifically written the song as a restless up-tempo. But Newman prevailed and, upon hearing the finished product, Rodgers was forced to admit that the song did indeed work splendidly as a ballad, so much so that it ultimately won the Academy Award® for Best Song of the Year.
Nearly all of the extensive fairground set was created on Fox's back lot and sound stages. A notable exception is the rollercoaster sequence that introduces Jeanne Crain to Dana Andrews. While all of the dialogue between the characters is clearly shot on a set, there are many glimpses of Andrews and Crain on the coaster.
Wayne Frake had practiced ring tossing for a year to get the money back he lost, amounting to $8 dollars, which doesn't sound like much now, but would be worth $143 as of 2025.