Jack Webb did before Dragnet (see also Pat Novak For Hire and Johnny Modero: Pier 23). Originally a Summer radio series, it debuted on CBS in July 1948. Webb played Jeff Regan, a rough-and-tough private eye working for the Los Angeles-based International Detective Bureau, run by Anthony J. Lyon. Regan introduced himself on each show "I get ten a day and expenses...they call me the Lion's Eye."
The show was fairly well-plotted, Webb's voice was great, and the supporting cast were skillful.
Regan handled rough assignments from Lyon, with whom he was not always on good terms. He was tough, tenacious, and had a dry sense of humor. The voice of his boss, Anthony Lyon, was Wilms Herbert. The show ended in December 1948 but was resurrected in October 1949 with a new cast; Frank Graham played Regan (later Paul Dubrov was the lead) and Frank Nelson portrayed Lyon. This version ran on CBS, sometimes as a West Coast regional, until August 1950. Both versions were 30 minutes, but the day and time slot changed several times. A total of 29 episodes from this series are in trading currency.
Info via http://www.thrillingdetective.com/regan.html
Frank Graham Episodes-