The Castle was Nashville's first commercial recording studio, producing close to half of the songs on the country music charts between 1947 and 1955.
[4] In 1946, recognizing demand for local recording studio services in Nashville, WSM broadcast engineers Carl Jenkins, George Reynolds and Aaron Shelton established Castle Recording Laboratory (named after the radio station's nickname "Air Castle of the South").
The engineers utilized an 8-input mono mixing console designed by Reynolds and WSM's facilities at the National Life and Accident Insurance Company Building at 7th Avenue North and Union Street after broadcast hours, with signals transferred via telephone line to a recording lathe at WSM's backup transmitter site 12 miles (19 km) away.
[4] In May, 1952, Kitty Wells recorded "It Wasn't God Who Made Honky Tonk Angels" at Castle Studio.
[10] Castle Recording Laboratory shut down in 1956 in light of WSM enacting new policies designed to limit employees' outside business interests, as well as the planned demolition of the Tulane Hotel.