USO tour

When she was 17, Lynn auditioned to participate in United Service Organizations entertainment. At age 18 she was part of a USO tour in the China Burma India Theater. She realized the gravity of the situation when a Marine gave her a pistol saying, "You might need this."

Her activities on the tour included visiting patients in hospitals and singing requests from a repertoire of 725 songs. She also met recently released prisoners of war from Rangoon, and she was told by a doctor, "Most of them will be out of their minds in six months."

On Broadway, she appeared in Walk with Music (1940), Oklahoma! (1943), and Park Avenue (1946). She was discovered in a Broadway production by Darryl F. Zanuck and signed to 20th Century Fox. A clause in her contract allowed the studio to drop her at six-month intervals, leading to recurring concerns for Lynn. She said, "I was a redhead with freckles and didn’t have a bosom. I prayed so hard they’d keep picking me up."