Dragnet, the radio series, premiered on NBC on June 3, 1949 and ended on February 26, 1957. A set of 314 original episodes aired between June 1949 and September 1955 with ".22 Rifle For Christmas" and "The Big Little Jesus" usually re-run during Christmas time. Re-runs were broadcast from the end of September 1955 to February 1957. The vast majority of the episodes are available free on various sites around the Internet.
References
List of Dragnet (radio series) episodes Wikipedia(Text) CC BY-SA