The old-time radio series 21st Precinct was a dramatic police procedural that aired on CBS from 1953 to 1956. It was a gritty, realistic police drama, often compared to the style of Dragnet. The show was known for its authentic, documentary-style approach to everyday police work, focusing heavily on procedure and the human element of policing.

• The series was set in the fictional 21st Precinct in New York City, described in the opening narration as "just lines on a map of the city of New York," a nine-tenths of a square mile area "between Fifth Avenue and the East River."
• Each episode typically began with a crime or incident reported by a phone call to the precinct desk. The story then followed the officers—from the initial response to the final report—detailing the investigation, which often involved not just the main crime but also the routine, personal, and professional problems of the officers.
• The primary character and narrator was the commanding officer, Captain Frank Kennelly, who served as the listener's guide through the day-to-day operations and challenges of the precinct. Everett Sloane played Captain Kennelly for the majority of the series.
• The show was produced with the official cooperation of the Patrolmen's Benevolent Association of the City of New York, and its stories were presented as adaptations of true criminal records, giving it an added layer of realism. The production used no theme or transitional music, instead relying on sound effects (typewriters, telephones, footsteps) to create an authentic atmosphere of the bustling police station.